The job, sometimes called the "trade czar," is expected to be a lynchpin position as Biden pledges to reverse predecessor Donald Trump's "America First" policies, build jobs at home, and punish Beijing for anti-competitive trade practices.

Tai played a key role in negotiating stronger labor provisions with the Trump administration in the new U.S.-Mexico-Canada (USMCA) trade deal, and has solid backing in labor and business circles, people familiar with the Biden team's deliberations say.

A Yale and Harvard-educated Chinese-American who speaks fluent Mandarin and taught university English for two years in Guangzhou, Tai also headed China trade enforcement at the U.S. Trade Representative's office (USTR) from 2011 to 2014, litigating trade violation cases before the World Trade Organization.

"Katherine Tai is the most qualified candidate for USTR, and I'm proud to support her," Senator Sherrod Brown, a Democrat on the trade- and tax-focused Senate Finance Committee, told Reuters in an emailed response to questions.

"She played a critical role in securing real improvements for workers in the USMCA agreement last year. She is uniquely prepared to tackle issues on China and knows how to partner with our allies to advance U.S. interests," Brown added.

On Wednesday, 10 House Democrats urged Biden to choose Tai, calling her "uniquely able to negotiate and advance priorities with both friendly and hostile negotiating partners" in a letter.

The top USTR job in the past has sometimes gone to those owed political favors or to prominent elected officials, with committee staff more likely to get a deputy-level position and assume a lot of the behind-the-scenes workload.

A groundswell of Capitol Hill support may help shift that practice under Biden, who has promised diversity as well as deep experience in his early Cabinet picks.

Tai, 45, did not respond to a request for comment and a spokeswoman for the House Ways and Means Committee said she was not granting interviews at this time. A spokesman for the Biden transition team also declined to comment.

Representative Earl Blumenauer, who chairs the House Ways and Means trade subcommittee, told Reuters Tai was "knowledgeable, patient, and creative," adding: "I would hate to lose her from our committee staff, but she would more than make up for it with what she could bring to the USTR."

PLAY 'OFFENSE' VS. CHINA

This August, Tai outlined a different approach to China than the 2-1/2-year punitive tariff war waged by current trade czar Robert Lighthizer at a Center for American Progress forum https://www.americanprogress.org/events/2020/07/30/488355/progressive-visions-trade.

The Trump administration has been "very strong on confronting China" she said, but such tariff actions were largely "defensive," and the United States needs a better offense.

"I think the offense has got to be about what we are going to do to make ourselves and our workers and our industries and our allies faster, nimbler, able to jump higher and able to compete stronger," Tai said.

Tai faces stiff competition for the USTR post from Michael Wessel, a member of the U.S.-China Economic and Security Review Commission, and Representative Jimmy Gomez, a Ways and Means Committee Democrat from California.

Representative Don Beyer, another Ways and Means Democrat who also favors Tai for USTR, said he believes House Speaker Nancy Pelosi was unlikely to agree to release any currently serving lawmakers to join the administration because this could jeopardize the razor-thin majority that Democrats hold in the House.

(Reporting by David Lawder and Andrea Shalal; additional reporting by Trevor Hunnicutt in Wilmington, Delaware; editing by Heather Timmons and Jonathan Oatis)

By David Lawder and Andrea Shalal