Sino-US Trade Tensions Cloud G20 Summit Outlook

World leaders gathered in Japan on Friday for one of the most high-stakes and fractious G20 meetings in years, with a bruising US-China trade war, geopolitical tensions, and climate change on the agenda.

The two-day summit in Osaka will be dominated by trade issues, with all eyes on whether President Xi Jinping and his US counterpart Donald Trump can reach a truce in a dispute that has been hugely damaging for the world economy.

But world leaders will also be seeking to tamp down tensions between Washington and Iran that have led to fears of a new conflict in the Middle East.

And they will look for common ground on climate change, with Japan hoping to unite European leaders who want strong action with an American leadership committed to withdrawing from the Paris climate agreement.

Trump set a combative tone even before arriving in Japan, taking aim at India, which he accused of seeking to increase tariffs on US goods.

And he said China was eager for a trade truce because its economy was "going down the tubes", appearing to also threaten another US$325 billion in levies in addition to the US$200 billion Washington has already imposed.

He struck a slightly more conciliatory tone on Friday morning, in brief remarks ahead of talks with Japan's Prime Minister Shinzo Abe.

"I know we are going to have a very successful day," the US leader said. He is scheduled for a long-awaited meeting with Xi on Saturday, his first since last year's G20.

Experts believe there is little chance of a full deal at the G20, saying the best hope is for a truce that would avoid Washington imposing new tariffs and ramping up the conflict.