World leaders including US President Joe Biden will seek to close ranks at back-to-back summits from Sunday on offering emphatic support to help Ukraine repel Russian invaders as the relentless war puts international unity to the test.

In the face-to-face talks, the allies will take stock of the effectiveness of sanctions imposed so far against Vladimir Putin's Russia, consider possible new military and financial aid for Ukraine, and begin turning their eye to longer-term reconstruction plans. 

But they will also be struggling to maintain a united front as the fallout from the war -- from soaring inflation to looming food shortages to fears over energy supplies -- tug at their resolve.

Ahead of the summit of G7 most industrialised nations which will be hosted from Sunday at the Bavarian mountain resort of Elmau Castle, German Chancellor Olaf Scholz warned that allies would need stamina in shoring up Ukraine. 

"The truth is, we are still far from negotiations between Ukraine and Russia" because Putin "still believes in the possibility of a dictated peace", Scholz said on Wednesday.

"It is therefore all the more important that we stay firmly on course -- with our sanctions, with internationally coordinated arms deliveries, with our financial support for Ukraine."

Scholz will be arriving in Elmau from an EU summit in Brussels, where the 27-member bloc on Thursday agreed to grant "candidate status" to Ukraine.

After the G7 summit closes on Tuesday, the leaders will head to a gathering of NATO powers in Madrid.

There, cracks are already apparent over Sweden and Finland's bids for accession, after Turkey blindsided the 30-member defence alliance in opposing the applications.

- 'Increase pressure' -

Western allies have supplied Ukraine with billions in financial aid and armaments, with the US leading the charge with $5.6 billion worth of weapons alone.

But as the war drags into its fifth month, Ukraine has repeatedly warned that it needs far more support to withstand the grinding Russian assault.

Ukraine's President Volodymyr Zelensky will participate in the G7 and NATO summits in separate video-link sessions, but he has made his agenda abundantly clear with his repeated pleas for more pressure on Russia and more weapons for his troops.

Washington said leaders at the G7 plan to "roll out a concrete set of proposals to increase pressure on Russia".

Yet allies' coordinated unprecedented action to shut down Russia's economy has failed so far to work.

Instead, it has exposed the Achilles heel of energy reliance that continues to crimp the ability of major players like Germany or Italy to go all out in punishing Moscow.

As the impact of Western sanctions start to trigger more violent aftershocks in the world economy, a backlash was also looming in other parts of the world.

Three invited guests at the G7 summit -- India, Senegal and South Africa -- have all shied away from condemning Russia over its invasion and all three face being hard hit by looming food shortages. 

A fourth guest, Indonesia, while voting for Russia to withdraw from Ukraine in a March UN vote, has refused to bar Putin from the G20 summit it is hosting in November. Instead, it has invited Zelensky too to attend.

Thorsten Brenner, director of the Global Public Policy Institute, noted that "a crucial task is convincing many non-Western countries who are sceptical of sanctions that the West is mindful of their concern about rising energy prices when designing sanctions".

"G7 also needs to make it clear that... the West lives up to its responsibility of advancing food security in most vulnerable countries."

- 'Not a catastrophe' -

Meanwhile in Madrid, where a broader spectrum of countries count among members, military support for Ukraine will be on the NATO agenda.

Here too, leaders will be keen to demonstrate their ironclad resolve to shield member states against Russia. 

But Turkey's opposition of Finland and Sweden's membership bids looks set to tarnish the show of unity.

The remaining 29 NATO leaders will seek to get Turkish President Recep Tayyip Erdogan to move towards a compromise but Germany has sought to manage expectations, saying it "would not be a catastrophe if we need a few more weeks" to reach an agreement.

The delay was an unwelcome distraction, and overshadows plans by the alliance to unveil plans to bolster its forces on its eastern flank with an eye to facing down Russia in the longer term.

NATO rushed tens of thousands of troops to eastern Europe in the wake of the invasion and members on Russia's borders were calling for major deployments to be stationed permanently as a new defensive wall.

But beyond Russia, the alliance will also update its "strategic concept" for the first time in a decade.

Crucially, it is not only expected to toughen its stance towards Russia but also mention the challenges posed by China for the first time.

EU grants candidate status to Ukraine

European Union leaders granted candidate status Thursday to Ukraine and Moldova in a strong show of support against Russia's invasion, as the United States said it was sending Kyiv more high-precision rocket systems.

The West's latest attempts to rally behind Ukraine came as Russia closed in on key cities in the country's embattled east and prompted growing global concerns with restrictions in gas and grain exports.

Ukraine's President Volodymyr Zelensky hailed the EU decision on his country and Moldova as "a unique and historic moment", although the two former Soviet republics face a long path before joining the bloc and its benefits of free movement and a common market.

"Ukraine's future is within the EU," said Zelensky, who had been working the phones for weeks.

"We will win, rebuild, enter the EU and then will rest. Or probably we will not rest."

French President Emmanuel Macron said that the decision by EU leaders sent a "very strong signal" to Russia that Europeans support the pro-Western aspirations of Ukraine.

President Vladimir Putin had declared Ukraine to be part of Moscow's sphere and insisted he was acting due to attempts to bring the country into NATO, the Western alliance that comes with security guarantees.

European powers before the invasion had distanced themselves from US support for Ukraine's NATO aspirations and EU membership is at least years away.

Ukraine and Moldova will have to go through protracted negotiations and the European Union has laid out steps that Kyiv must take even before that, including bolstering the rule of law and fighting corruption.

- Weapons to fight Russian gains -

The White House announced that it was sending another $450 million in fresh weapons to Ukraine including new High Mobility Artillery Rocket systems, which have been at the top of Kyiv's wish list.

The so-called Himars system can simultaneously launch multiple precision missiles at an extended range.

An initial four units have already been delivered, with Ukrainian soldiers being trained to operate the equipment, after President Joe Biden's administration said Kyiv had offered assurances it would not fire into Russia.

Ukraine's needs have been increasingly urgent as Russia -- which failed to take Kyiv immediately after invading on February 24 -- advances in the east, tightening its grip on strategically important Severodonetsk and its twin city Lysychansk across the Donets river.

Taking the cities would give Moscow control of the whole of Lugansk, allowing Russia to press further into the Donbas region and potentially farther west.

Ukraine acknowledged Thursday that it had lost control of two areas from where it was defending the cities, with Russian forces now closer to encircling the industrial hubs.

Britain's defence ministry said some Ukrainian units had probably been forced to withdraw "to avoid being encircled". 

"Russia's improved performance in this sector is likely a result of recent unit reinforcement and heavy concentration of fire," it said in its latest intelligence update.

A representative of pro-Russian separatists in Ukraine told AFP the resistance of Ukrainian forces trying to defend Lysychansk and Severodonetsk was "pointless and futile."

"At the rate our soldiers are going, very soon the whole territory of the Lugansk People's Republic will be liberated," said Andrei Marochko, a spokesman for the army of Lugansk.

The Russian army also said Thursday that its bombings in the southern city of Mykolaiv had destroyed 49 fuel storage tanks and three tank repair depots, after strikes killed several Ukrainian troops Wednesday.

- 'Only grannies left' -

The northeastern city of Kharkiv near the Russian border was nearly empty on Wednesday, AFP reporters said, a day after shelling by Moscow's forces killed five people there.

"Last night the building next to mine collapsed from the bombardment while I was sleeping," said Leyla Shoydhry, a young woman in a park near the opera house.

Roman Pohuliay, a 19-year-old in a pink sweatshirt, said most residents had fled the city.

"Only the grannies are left," he said.

In the central city of Zaporizhzhia, women were training to use Kalashnikov assault rifles in urban combat as Russian forces edged nearer.

"When you can do something, it's not so scary to take a machine gun in your hands," said Ulyana Kiyashko, 29, after moving through an improvised combat zone in a basement.

- 'Weaponising' grain and gas -

Western officials have also accused Russia of weaponising its key exports of gas as well as grain from Ukraine, contributing to global inflation and rising hunger in the world.

"We are very clear that this grain crisis is urgent, that it needs to be solved within the next month," British Foreign Secretary Liz Truss said on a visit to Turkey.

"Otherwise we could see devastating consequences," she said.

Ukraine's Foreign Minister Dmytro Kuleba urged African nations to pressure Russia for a safe route for grain.

"African capitals matter and they do influence Russia's position," he told African journalists.

A US official warned of new retaliatory measures against Russia at the Group of Seven summit being attended by Biden in Germany starting Sunday.

Germany ratcheted up an emergency gas plan to its second alert level, just one short of the maximum that could require rationing in Europe's largest economy, after Russia slashed its supplies.

"Gas is now a scarce commodity," Economy Minister Robert Habeck told reporters, urging households to cut back on use. Demand for gas is lower in the summer but shortages could cause heating shortages in the winter.

France is aiming to have its gas storage reserves at full capacity by early autumn, and will build a new floating methane terminal to get more energy supplies by sea, Prime Minister Elisabeth Borne said.

A Kremlin spokesman reiterated its claim that the supply cuts were due to maintenance and that necessary equipment from abroad had not arrived.