Only China can explain the reason for the absence of President Xi Jinping from the annual G20 summit in New Delhi this weekend, a U.S. official said on Saturday.

The summit had been seen as affording a venue for a possible meeting between Xi and U.S. President Joe Biden following months of efforts by the two world powers to mend ties frayed by trade and geopolitical tensions.

"It's incumbent upon the Chinese government to explain" why its leader "would or would not participate," Jon Finer, the U.S. deputy national security adviser, told reporters in the Indian capital.

Although the United States was often called upon to explain the actions of the Chinese government, that was not its role, he said, adding that it was "unfortunate" if China was not committed to the success of the bloc.

"Some have speculated China's absence indicates that it is giving up on the G20, building an alternative world order, that it will privilege groupings like the BRICS," Finer said.

Premier Li Qiang is leading China's delegation in the Indian capital. Also absent from the summit is President Vladimir Putin of Russia, which is being represented instead by Foreign Minister Sergei Lavrov.

Biden arrived on Friday for the summit.

Last Sunday, reacting to news that Xi would not attend the G20 summit, Biden said he was "disappointed" but would "get to see him."

India, the chair of the summit, along with the next two, Brazil and South Africa, as well as the United States, were committed to its success, Finer added.

"If China does not, that's unfortunate for everyone," he added. "But much more unfortunate, we believe, for China."