Katherine Tai, U.S. President Joe Biden's top trade nominee, backed tariffs as a "legitimate tool" to counter China's state-driven economic model and vowed to hold Beijing to its prior commitments, while promising a sweeping new approach to U.S. trade.

At her Senate confirmation hearing to become U.S. trade representative, Tai also called for a revamp of global trade rules to eliminate what she called "gray areas" exploited by China and end a "race to the bottom" that she said has hurt workers and the environment.

"For a very long time our trade policies were based on the assumption that the more we traded with each other, and more liberalized our trade, the more peace and prosperity there would be," Tai said, adding that trade liberalization in the past too often led to less prosperity, as well as lower labor and environmental standards.