WASHINGTON (AP) — President Joe Biden courted the support of the powerful International Brotherhood of Teamsters on Tuesday, reminding its leaders and members of his record on unions as likely Republican challenger Donald Trump tries to make gains among the blue-collar workers that helped propel his 2016 victory.

Biden met with the Teamsters at its headquarters and emphasized the administration's support of unions and his longtime support for the labor movement. Teamsters General President Sean O'Brien said after the meeting that Biden has been "great" for workers but stressed that "there's still a lot of work to be done" to bolster unions.

"There's always a threat to organized labor, so we want to be proactive and make certain every candidate — not just President Biden — understands how important our issues are," O'Brien told reporters after meeting with the president.

Biden and the Teamsters discussed topics such as the Butch Lewis Act — a measure now signed into law that shored up pensions for scores of workers — Social Security and Medicare, while the president vowed to continue to "hold corporations accountable, because every worker deserves respect, and billionaire executives shouldn't pay a lower tax rate than truck drivers or warehouse workers," said Biden campaign spokesperson Lauren Hitt.

Biden met privately with the Teamsters nearly six weeks after Trump sat down with them to earn their support. Emerging from that meeting, Trump boasted that a significant chunk of union voters has backed him and said of a possible Teamsters endorsement: "Stranger things have happened."

The president wants to harness labor's power and reach to bolster his campaign's efforts this year, as Trump tries to make inroads with union workers who have traditionally backed Democratic candidates. The former Republican president peeled away some blue-collar workers in his 2016 win and is looking to exploit a divide between union leaders who have backed Democratic candidates and rank-and-file members who could be swayed to vote Republican.

Union members tend to vote Democratic, with 56% of members and households backing Biden in 2020, according to AP VoteCast. Biden, who regularly touts himself as the most pro-union president in history, has swept up endorsements from leading labor groups such as the AFL-CIO, the American Federation of Teachers and the American Federation of State, County and Municipal Employees.

"The Biden-Harris campaign is proud to have the support of the AFL-CIO, AFSCME, AFT, UAW and many other unions," said Hitt. "We hope to earn the support of the Teamsters as well."

It's not just the support of the Teamsters that Biden and Trump has battled over. The Democratic president traveled to Michigan last September and joined striking autoworkers, becoming the first president in modern history to join an active picket line.

The United Auto Workers later formally endorsed Biden, even as Trump made his own trips to Michigan to criticize the president's push for more electric vehicles – one of the union's chief concerns during their strike. Trump, however, had made his Michigan appearance at a non-unionized auto parts plant.

The Teamsters union represents 1.3 million workers. It backed Hillary Clinton in 2016 and Biden in 2020, although O'Brien has stressed that the union is keeping an open mind on endorsements this cycle. The group generally waits until after both parties' summer nominating conventions to make a formal endorsement, and will "most likely" do so again this year, once it polls its members, solicits rank-and-file input, and reconvenes its leadership team, O'Brien said.

The union's membership includes UPS drivers, film and television workers, freight operators, members of law enforcement and other government workers.

"The Teamsters union is good at one thing: mobilizing our members, especially when a decision and/or battle needs to be had," O'Brien said, adding: "We have proven how valuable our members are and how engaged — more importantly — they are."