WASHINGTON, April 5 (Reuters) - The U.S. nominee to run the World Bank, Ajay Banga, said on Wednesday that he supports the bank's proposal to expand its annual lending capacity by about $5 billion to help tackle climate change and other global challenges, but that was only the start of reforms.

Banga, the former CEO of Mastercard and the sole contender for the bank's top job, told an event hosted by the Center for Global Development that he had high ambitions for reforming the world's largest development lender.

"That's good, we should do it," he said of the $5 billion lending expansion plan. "Maybe we can get a little more or even a lot more with the next set of steps. Whatever the amount may be, we have to put our balance sheet to work." (Reporting by David Lawder, Editing by Franklin Paul)