The president of the Teamsters union has asked for speaking slots at both the Republican and Democratic national conventions, at a time when President Joe Biden and former President Donald Trump have pressed for support from rank-and-file members of organized labor.

The move by Sean O’Brien, president of the International Brotherhood of Teamsters, underscores the fact that his group, unlike other influential umbrella unions that have backed Biden in the 2024 election, has yet to endorse in the presidential race. O’Brien has made clear he is delaying a decision until later this year.

Kara Deniz, a spokesperson for the Teamsters union, confirmed that O’Brien, through aides, has told officials working on both conventions that he would be interested in speaking at their dayslong nomination events. The Republicans will hold their convention in Milwaukee in July, and the Democrats will hold theirs in Chicago in August.

It would be unusual in the current fractious political climate for someone to speak at both conventions.

Over the course of the year, O’Brien has invited several presidential candidates, including Biden, Trump and independent candidates like Cornel West and Robert F. Kennedy Jr., to speak before his group.

The Teamsters is one of the country’s largest labor unions, with 1.3 million members in sectors such as trucking and manufacturing. The AFL-CIO and the United Auto Workers have backed Biden, and Shawn Fain, president of the UAW, has been harshly critical of Trump.

O’Brien had a private meeting with Trump at the beginning of the year at Mar-a-Lago in Palm Beach, Florida, shortly before the Iowa caucuses that the former president won handily, setting him on a path to become his party’s nominee for a third time.

Biden has described himself as the most pro- labor president in history.

The Teamsters endorsed Biden in 2020, although their support came relatively late in the general election campaign, well after it was clear that the then-candidate would be the presumptive Democratic nominee.