WASHINGTON (AP) — The White House is hoping that Julie Su's role in brokering a deal between West Coast dockworkers and shippers will provide fresh momentum for the Senate to act on her long-stalled nomination to be labor secretary.

Su flew to San Francisco to help seal the tentative agreement after a lengthy dispute that had led to sporadic disruptions at some of the nation’s largest ports. President Joe Biden asked Su, a civil rights lawyer who was deputy labor secretary when tapped for the Cabinet job in February, to join the negotiations, according to a White House official, in an effort to stave off potential work stoppages as the bargaining sessions grew tense.

Biden thanked Su, the department's acting head, and said he had relied on her “deep expertise and judgment” to move the negotiations along.

“This is going to have a real positive impact on trade,” Biden said. “She's shown she's a true leader and I think she should be confirmed.”

The International Longshore and Warehouse Union and the Pacific Maritime Association said Su played a key role in finalizing the deal. The U.S. Chamber of Commerce praised Su for “staying committed to the process and helping both parties reach this agreement.”

White House officials hope her participation could sway Senate holdouts who had questioned her experience in negotiations between workers and management and wondered whether she was anti-business.

Su's nomination cleared a key Senate committee in April, but with no Republicans on record supporting her, the Biden administration and her backers have scrambled to lock down 50 Democratic votes needed to confirm her. For weeks, several moderate Democrats have refused to say whether they would vote for her.

There's deep skepticism that Sen. Joe Manchin, D-W.Va., will vote “yes,” particularly considering that this week he rejected three Biden nominees endorsed by all other Democrats but uniformly opposed by GOP senators. Sen. Kyrsten Sinema, an Arizona independent, is an important ally of business groups and some Su supporters have been concerned she could reject a nominee viewed as too close to unions.

Su has come under criticism from business organizations about her stewardship of California's labor department.

She backed a now-overturned law that would have required app-based ride hailing and delivery companies such as Uber and Lyft, as well as trucking businesses, to treat their workers as employees, providing paid sick leave and unemployment insurance, for example, rather than as independent contractors.

Su has also faced blame for problems at the agency during the pandemic when unprecedented numbers of people applying for unemployment benefits faced long wait times and the state paid out billions of dollars in fraudulent claims.

Illinois Sen. Dick Durbin, the second-ranking Democrat, said this week that he was still trying to win over two or three more Democrats.

“They’ve said probably no, but not never," Durbin said. "So we’re talking to them.”

Sen. Jon Tester, D-Mont., who has not said where he stands, said Thursday that he was “taking input from folks.” But he also expressed frustration with the situation. “I wish we would have a vote so people would vote and move on," Tester said. “Up or down, whatever it might be.”

Installing Su is a priority for unions that are vital Biden allies and for Asian American advocacy groups, miffed that his administration was the first in 20 years not to have an Asian American in the Cabinet. Su, a daughter of Chinese immigrants, has spoken emotionally about her mother emigrating to the United States on a cargo ship, unable to pay for a passenger ticket.

Top White House officials have been holding daily strategy calls about how to win her confirmation. Chief of staff Jeff Zients and Louisa Terrell, director of legislative affairs, speak regularly with Senate Majority Leader Chuck Schumer, D-N.Y., on the matter. Biden's first labor secretary, Marty Walsh, has advocated for Su in private with senators.

Republicans are working to foment opposition. Sen. Bill Cassidy, R-La., wrote Su this week about the stalled dockworkers negotiations before a deal was announced, asserting that she had “no clear track record of working with labor and management to end labor disputes.”

The tentative agreement, which would affect 22,000 dockworkers at 29 ports along the West Coast, must be ratified by both sides. They did not disclose terms of the deal. Dockworkers have operated without a contract since July.

Su said in a statement that the pact showed “once again that collective bargaining — though sometimes difficult — works.”