Hours before Joe Biden hits the campaign trail for the first time as a 2020 Democratic presidential candidate, the former vice president landed his first major endorsement.

The International Association of Fire Fighters (IAFF) announced Monday morning that they’re endorsing Biden, who has long and strong ties to the union and to the organized labor movement in general.

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"On behalf of the International Association of Fire Fighters, I'm proud to announce that we stand with Joe Biden and endorse his candidacy for President of the United States," IAFF general president Harold Schaitberger highlighted in a video.

Schaitberger emphasized that "Joe's a lot like our firefighters. He's a problem solver who cares deeply about America and committed to making our country better. He's one of the staunchest advocates for working families.”

The endorsement by the IAFF – which sat on the sidelines in the 2016 general election – is the first by a major union this presidential cycle.

Speaking to "Fox & Friends" on Monday, Schaitberger offered further explanation on why the union is backing Biden.

He said Biden has been a supporter of the union, which represents 316,000 full-time firefighters, for more than 40 years.

“We’re loyal,” Schaitberger said. “We respect and reward those who stand with us. In this case, we’re standing with Joe Biden.”

The IAFF’s backing comes hours before Biden was scheduled to give the first major speech of his presidential campaign – his third White House bid – at a Teamsters banquet hall in Pittsburgh, Pennsylvania. The event kicks off the former vice president’s six-state swing over three weeks. That trip is expected to end with a major speech in Philadelphia.

The start and finish of his initial campaign swing in Pennsylvania is no surprise. The state – long a crucial battleground in presidential elections – was one of the key working-class Rust Belt states Republican President Trump flipped in the 2016 election to help him capture the White House.

And while Biden has long lived in Delaware and represented that state for nearly four decades in the Senate, he was born and spent his early years in Scranton, Pennsylvania, and the Keystone State has always remained special to him. The stops in Pennsylvania are meant to signal that Biden is determined to recapture working-class voters swayed by Trump’s populist message in 2016. Just a few days before he launched his campaign last week, Biden traveled to Boston to support and address striking Stop and Shop supermarket employees.

Biden gave a major hint of his impending presidential run as he spoke in front of the IAFF at their annual convention in Washington, D.C., in March. Biden was greeted with chants of “run Joe, run” as he took the podium.

A few minutes later, during his keynote address, Biden said: “I appreciate the energy you showed when I got up here. Save it a little longer. I may need it in a few weeks.”

The comment brought a standing ovation from the audience.

“Be careful what you wish for,” Biden joked. “Be careful what you wish for.”

While there’s been a decline in union membership in recent decades, they still remain a powerful political force, especially in Democratic Party politics. The IAFF, which was formed a century ago, includes more than 316,000 members across more than 3,200 affiliate organizations. Its political action committee is one of the most active and potent in the country.