US President Joe Biden arrives at this weekend's Group of 20 (G20) meeting in India with an offer for the "Global South": whatever happens to China's economy, the United States can help fund your development.

Armed with cash for the World Bank and promises of sustained U.S. engagement, Biden hopes to persuade fast-growing economies in Africa, Latin America and Asia that there is an alternative to China's Belt and Road project, which has funneled billions of dollars to developing countries but left many deeply in debt.

He will have at least one advantage: Chinese President Xi Jinping will not be at the meetings.

While Biden said he was "disappointed", Xi's absence as China's economy wobbles creates a narrow opening for Washington to reshape the agenda of a political club it has struggled to corral.

At the heart of Biden's pitch are World Bank reform proposals and stepped-up funding for the lender's climate and infrastructure aid in the developing world, which would free up hundreds of billions of dollars in new funding for grants and loans.

The White House is seeking $3.3 billion from Congress to complement earlier steps by the U.S. and close allies to raise $600 billion by 2027 in public and private money for the Partnership for Global Infrastructure and Investment, a Belt and Road alternative that excludes China.

"Xi's absence from the G20 does give the United States an opening, which could be compounded by the challenges that China's economic downturn will have for Belt and Road spending," said Zack Cooper, a senior fellow focused on Asia at the American Enterprise Institute.

"But the question ... is whether the United States will be able to step up."