President Joe Biden’s trade chief called tariffs an “important defensive tool” for rebalancing unfair commercial relationships, a nod to the value of duties on exports from China as the administration considers changes.

US Trade Representative Katherine Tai said on Tuesday that while the tariffs are “the least interesting aspect” of a complex trade and economic relationship with China, the US has long relied on such duties as a “playing field leveler.”

The comments, in a discussion about China during an interview at the University of Chicago Institute of Politics, come as the White House evaluates the future of import taxes on more than $300 billion in Chinese goods first imposed by then President Donald Trump more than five years ago. Tai has previously underlined how the tariffs provide leverage to persuade Beijing to change what the US considers unfair practices.

US Trade Representative Katherine Tai

The Biden administration has spent years deciding the fate of the duties created to pressure Beijing, which the US said was stealing intellectual property and forcing American companies to transfer their technology. The US has been considering a potential increase in tariffs on Chinese electric vehicles and other goods.

The current duties span imports from industrial inputs, such as microchips and chemicals, to consumer merchandise including apparel and furniture. Trump imposed the first of the tariffs in 2018, citing section 301 of the Trade Act of 1974.

Trump, the front-runner for the 2024 Republican presidential nomination, has been talking in an increasingly hawkish way about China on the campaign trail, saying that he might impose a tariff of more than 60% on the nation’s goods.

Curbing economic ties between the world’s two largest economies is gaining support from some US lawmakers, led by Republican Representative Mike Gallagher and Democrat Raja Krishnamoorthi, who recommended raising tariffs and restricting Chinese investment in a House committee report in December.