WASHINGTON — Katherine Tai, President Biden’s pick for United States trade representative, promised lawmakers during her confirmation hearing on Thursday that she would work with Congress to help reinvigorate the economy and aggressively enforce American trade rules against China, Mexico and other trading partners.

Ms. Tai, in testimony before the Senate Finance Committee, said her background challenging China’s unfair trade practices in the Obama administration had given her knowledge of “the opportunities and limitations in our existing toolbox.” She promised to work with allies and enforce the terms of the trade deal that President Donald J. Trump signed with Beijing last year, while working to develop a more “strategic and coherent plan” for competing with China’s state-directed economy.

As trade representative, Ms. Tai would work toward several of the Biden administration’s key goals, including helping to restore American alliances abroad and reforming and enforcing American trade rules to help alleviate inequality and mitigate climate change.

In her testimony Thursday morning, Ms. Tai promised to ensure that trading partners adhered to new trade rules, including the agreement that Mr. Trump signed with China last year and new measures included in the revised North American trade deal, the United States-Mexico-Canada Agreement.

She declined to give many specifics on the trade policies the Biden administration would pursue, saying instead she would review existing tariffs and trade negotiations. But she laid out a philosophy on trade that would support broader, more equitable growth and “recognize that people are workers and wage earners, not just consumers,” which she said would be a significant departure from the past.

Mr. Biden and other Democrats have complained that the trade policies of previous presidents were often driven by the interests of corporations and lobbyists, and ended up surrendering the interests of lower-wage workers for the benefit of certain businesses and exporters.

Trade policy for the past several decades had often fallen “into a pattern where one sector of our economy and one segment of our workers feel like their livelihoods and their opportunities are sacrificed to another part of our economy,” Ms. Tai said.

She said the administration would try “to break out of that pattern, so that what we are doing in trade is coordinated with what we are doing in other areas, but also not forcing us to pit one of our segments of our workers and our economy against another.”

Asked about the tariffs that Mr. Trump had placed on foreign metals, Ms. Tai said that tariffs were “a legitimate tool in the trade toolbox,” but that the global steel and aluminum industries faced larger problems with overcapacity that might require other policy solutions. She also said that she was aware of “the many concerns” that had arisen with the process of companies applying for exclusions from the tariffs, and said that reviewing that system with an eye to transparency, predictability and due process would be “very high on my radar.”

Ms. Tai most recently worked as the chief trade counsel of the House Ways and Means Committee, where she helped to hammer out reforms that ultimately brought Democrats on board with U.S.M.C.A., which was negotiated by Mr. Trump. Before that, she served in the trade representative’s general counsel office, where she brought several successful cases against China’s trade practices at the World Trade Organization.

If confirmed, Ms. Tai would be the first woman of color and first Asian-American to serve in the position.

Ms. Tai also said that she wanted take a role in a new Biden administration effort to strengthen critical supply chains, saying that past trade policy had focused on efficiency rather than resilience, and needed to be rethought. She said that she shared the Trump administration’s goal of bringing supply chains back to America, but that the prior administration’s policies had created “a lot of disruption and consternation,” adding, “I’d want to accomplish similar goals in a more effective, process-driven manner.”

She pledged to re-engage the United States at the World Trade Organization, which the Trump administration largely bypassed or ignored, but acknowledged that the global trade group faced big challenges to its effectiveness.

The United States can’t afford not to be a leader in the organization, she said, but “the W.T.O. does need reform.”

Ms. Tai also expressed interest in resolving a long-running trade dispute between the European Union and the United States at the World Trade Organization over subsidies given to the plane makers Boeing and Airbus, which has resulted in a volley of tariffs.

“If confirmed, I would very much be interested in figuring out — pardon the pun — how to land this particular plane,” Ms. Tai said.

Senators of both parties were mostly complimentary of Ms. Tai’s experience and trade knowledge, though several Republican senators expressed concerns about her failure to commit to free trade in principle, and to pledge to aggressively drive forward new trade negotiations.

Senator Mike Crapo, a Republican from Idaho, praised Ms. Tai’s extensive experience in trade, but raised concerns about Mr. Biden’s pledges to address domestic priorities first before signing any new trade deals.

“Our businesses and workers are ready to sell American to all foreign customers right now,” Mr. Crapo said. “Our businesses need that access more than ever because other countries are not standing still.”

Ms. Tai said she planned to review the trade negotiations with Britain, saying that the country’s departure from Europe, the coronavirus pandemic and other developments since negotiations started in 2018 demanded new consideration.

Asked about rejoining the Trans-Pacific Partnership, a multicountry trade deal negotiated by President Obama that Mr. Trump withdrew from, Ms. Tai said that she would work with like-minded countries in the Asia-Pacific on the issue of China, but stopped short of calling for rejoining the T.P.P.

The “basic formula for the T.P.P.,” of the United States engaging with countries with shared strategic and economic interests with the challenge of China in mind “is still a sound formulation,” she said.

“I think what I would add is a lot has changed in the world in the past five or six years, and a lot has changed in terms of our own awareness of some of the pitfalls of the trade policies that we’ve pursued as we’ve pursued them over the most recent years.”