President Joe Biden said Thursday that he was “concerned” Boeing had locked out its firefighters and urged the airplane manufacturer to reach a deal with the workers’ union as soon as possible.

Boeing forced 125 firefighters and other first responders in Washington State off the job early Saturday morning amid a dispute over a new contract. The union, the International Association of Fire Fighters, accused the company of “choosing corporate greed over safety.”

Biden stepped into the feud with a post on X, formerly known as Twitter, Thursday afternoon:

A lockout is a work stoppage initiated by the employer rather than the workers, with the aim of gaining leverage in contract talks.

The firefighters’ previous agreement with Boeing recently expired, and the two sides failed to come to terms on a new one. Boeing maintains that it made two competitive offers to the union, but the IAFF said the proposals would leave firefighters with pay and benefits well behind local municipal fire departments.

The union accused Boeing of using the lockout to “punish, intimidate, and coerce its firefighters into accepting a contract that undervalues their work.”

It’s been a tough year so far for Boeing. The company hasn’t managed to escape the news ever since a door panel blew out on an Alaska Airlines 737 Max jet in January, prompting Congressional hearings on Boeing’s safety practices and an audit by the Federal Aviation Administration. Boeing CEO Dave Calhoun recently announced he would resign at the end of the year.

Boeing said in a statement Thursday that its offer “provides significant pay increases and increased benefits.”

“We remain committed to securing an agreement,” the company said.

Biden has shown a far greater willingness than his predecessors to wade into union matters at individual companies.

Earlier this year he voiced his support for Volkswagen workers who were trying to unionize their Tennessee factory, and publicly congratulated them when they won their election last month. In 2021, he gave a speech denouncing union-busting in the context of a closely watched election at an Amazon warehouse in Alabama. He often touts himself as “the most pro-union” president in history.

Biden’s relationship with the firefighters’ union goes back years. The IAFF was the first major union to endorse Biden during his 2020 run for the White House, and the president spoke at the union’s conference in Washington last year.

The IAFF has not yet announced an endorsement for president this year.

This story has been updated with comment from Boeing.