Critics of Ukraine's slow progress on the battlefield against Moscow's troops should "shut up", the country's foreign minister said Thursday as he attended a meeting of EU counterparts.

"Criticizing the slow pace of the counteroffensive equals to spitting into the face of the Ukrainian soldier who sacrifices his life every day," Dmytro Kuleba told reporters on sidelines of the EU ministerial meeting held in Toledo, Spain.

"I would recommend all critics to shut up, come to Ukraine and try to liberate one square centimetre by themselves," he said.

The furious words came after Kuleba thanked EU ministers for their governments' support so far, and urged them to supply Ukraine with more lethal weapons, long-range missiles, armoured vehicles and air defence systems.

Western capitals, which have already supplied Ukraine with weapons and munitions, have noted the slow and costly pace of the push back against dug-in Russian forces but insist they are sticking with Kyiv for the long term.

Kuleba also said an upcoming September meeting between Russian President Vladimir Putin and Turkish President Recep Tayyip Erdogan for talks on reviving a Black Sea grain deal was "almost a last chance" for Moscow to come back into the pact.

He talked up an "alternative sea grain corridor" running along Romania's Black Sea coast, but said air defence systems were needed to protect ships carrying grain before they entered those waters.