WASHINGTON - Janet Yellen, US President-elect Joe Biden's nominee for treasury secretary, said on Tuesday that the United States does not seek a weaker dollar to gain competitive advantage.

"I believe in market determined exchange rates. The value of the US dollar and other currency should be determined by markets. Markets adjust to reflect variations in economic performance and generally facilitate adjustments in the global economy," Yellen said at her confirmation hearing virtually held by the Senate Finance Committee.

"The United States does not seek a weaker currency to gain competitive advantage, and we should oppose attempts by other countries to do so. The intentional targeting of exchange rates to gain commercial advantage is unacceptable," she said.

If confirmed by the Senate, Yellen said she will work to "oppose any and all attempts by foreign countries to artificially manipulate currency values to gain an unfair advantage in trade".

Yellen's remarks came after the US Trade Representative (USTR)'s Office last week claimed that Vietnam's acts, policies and practices related to currency valuation are "unreasonable" and restrict US commerce. It's not clear whether the Biden administration would take any actions regarding Vietnam's currency practices.

Yellen, a well-regarded economist and former central bank official, is not expected to face any serious opposition from US senators. If confirmed, she would be the first woman to serve as US treasury secretary in the department's 231 years of history. She would also be the first person to have served as treasury secretary, chair of the Council of Economic Advisors, and chair of the Federal Reserve.