A U.S. Treasury official says China has made progress allowing its currency to rise against the dollar but greater flexibility is needed.

Lael Brainard, the Treasury Department's undersecretary for international affairs, praised China's recent efforts to allow the yuan to rise and fall by a slightly wider margin against the dollar in daily trading. But Brainard says China must "go forward" on cutting tariffs and opening its financial markets to foreign firms.

"We'll continue to push very hard on that," Brainard says.

Critics, including members of Congress, say China has undervalued its currency against the dollar. That has made Chinese goods cheaper in the U.S. and American products more expensive in China.

Brainard spoke Monday ahead of the Asia-Pacific Economic Cooperation meeting in Moscow later this week.