US President Joe Biden arrived in Indonesia's Bali on Sunday for a summit of the world's 20 largest economies and a high-stakes meeting with Chinese leader Xi Jinping.

The US leader said he expects to establish "red lines" in Washington's fraught relations with Beijing in his first face-to-face talks as president with Xi.

The superpower sit-down will come on the sidelines of the G20 summit from Monday, the biggest gathering by the group since the Covid-19 pandemic began.

Biden said he was going into the discussions with Xi "stronger", after his Democratic Party's unexpected success in midterm elections they had been forecast to lose heavily.

But the summit comes with Beijing and Washington's rivalry intensifying as a more powerful and assertive China tries to disrupt the US-led international order.

The world's two largest economies are at loggerheads on everything from trade to human rights in China's Xinjiang region and the status of the self-ruled island of Taiwan, and Biden said he expected "straightforward discussions" with Xi.

"I know Xi Jinping, he knows me," he told reporters in Phnom Penh where he met with Asian leaders before heading to the Indonesian resort island of Bali.

"We have very little misunderstanding. We just got to figure out what the red lines are," Biden said.

Biden hopes to "come out of this meeting with areas where the two countries and the two presidents and their teams can work cooperatively on substantive issues, National Security Advisor Jake Sullivan told reporters as the US leader flew to Bali.

He will push China to rein in North Korea after a record-breaking series of missile tests fuelled expectations that Pyongyang will soon carry out its seventh nuclear test.

- Putin stays away -
 

China is North Korea's main ally and while Biden is not expected to make demands, he will warn Xi that further missile and nuclear build-up would mean the United States boosting its military presence in the region -- something Beijing bitterly opposes.

Biden met Japan and South Korea's leaders before flying to Bali, with the allies pledging a "strong and resolute response" to any North Korean nuclear test.

The US-China talks will cast a long shadow over the first post-pandemic G20, a reunion that Russian President Vladimir Putin has pointedly opted to skip.

He instead sent his Foreign Minister Sergei Lavrov, who arrived earlier on Sunday.

Putin's invasion of Ukraine has made the trip to Bali logistically difficult and politically fraught, and while the war is not officially on the summit agenda, the conflict will dominate discussions.

Soaring energy and food prices have hit richer and poorer G20 members alike -– and both are directly fuelled by the war.

There is likely to be pressure on Russia to extend a deal allowing Ukrainian grain and fertiliser shipments through the Black Sea when the current agreement expires on November 19.

- 'Never been this complex' -
 

At a minimum, Biden and his allies want the G20 to make it clear to Putin that nuclear war is unacceptable.

Even that once uncontroversial position is likely to be blocked by a mixture of Russian opposition and Chinese unwillingness to break ranks with its ally in Moscow or give Washington a win.

At a recent meeting with German Chancellor Olaf Scholz, Xi said a nuclear war could not be won and should never be fought.

Ryan Hass, a former director for China at the US National Security Council, said Xi "likely will not be as magnanimous in his meeting with Biden".

"He will not want to be perceived as satisfying a request from Biden, whether on Ukraine, nuclear use, North Korea, or any other issue," Hass told AFP.

G20 host Indonesia -- still careful not to favour either China or the United States -- is not confident that the leaders will be able to break the deadlock.

Ministerial meetings hosted by Indonesia in the run-up to the summit have failed to agree on a final joint communique -- a procedural-sounding tradition that can be important in driving cooperation.

"Honestly, I think the global situation has never been this complex," said Indonesian government minister Luhut Binsar Pandjaitan on the eve of the summit.

"If eventually (the G20) leaders do not produce a communique, that's that, it's OK."