US sanctions on China over Ukraine not 'necessary or appropriate': Yellen

US Treasury Secretary Janet Yellen said Friday that sanctions against China are "not necessary or appropriate" since its support for Russia following the invasion of Ukraine was still unclear.

"I don't think that that's necessary or appropriate at this point," Yellen said in an interview with CNBC, adding that "senior administration officials are talking privately quietly with China to make sure that they understand our position."

She noted Washington "would be very concerned if they were to supply weapons to Russia. Or to try to evade the sanctions that we've put in place on the Russian financial system and the central bank. We don't see that happening at this point."

Yellen also warned that gasoline prices could rise further in the United States, where inflation is already at a rate not seen since the 1980s, sapping President Joe Biden's popularity.

"It's conceivable that they could move higher," she said, but said the administration is trying to ensure adequate supplies of oil and natural gas, and also aid its European allies.

"But when the 11th-largest economy faces sanctions because of their horrific behavior in Ukraine, there just are going to be spillovers that are unavoidable," she said.