WASHINGTON (AP) — Vice President Mike Pence has called his soon-to-be successor Kamala Harris to offer his congratulations, according to two people familiar with the conversation.

It's the first known contact between the elected members of the outgoing and incoming administrations. President Donald Trump has not reached out to President-elect Joe Biden or invited him to the White House, and has instead spent the weeks since he lost the Nov. 3 election holed up at the White House, trying to undermine the legitimacy of Biden’s win with baseless claims of mass voter fraud that culminated in last week's violent storming of the Capitol building.

Pence, who didn't speak with Trump for days after the siege, has become an unexpected — albeit late — defender of Biden's win. The vice president resisted enormous pressure from Trump to try to interfere in Congress' certification of the Electoral College vote count last week — even though he has no such power. And he has announced that he will attend Biden’s Jan. 20 inauguration, which Trump is refusing to do — making him just the fourth president in the nation's history to skip the symbolic passing of the torch.

Pence and Harris spoke Thursday afternoon and had a “good call," according to one of the people familiar with the conversation, with Pence congratulating Harris and offering his assistance. The people spoke on condition of anonymity to describe the private exchange.

The call came less than a week before Biden and Harris take office and just over a week after Trump supporters violently stormed the Capitol and tried to halt the peaceful transition of power after he delivered a speech calling on them to “fight.” Five people died, including a Capitol Police officer, and Trump got impeached on a charge of incitement of an insurrection.

While Trump has remained largely behind closed doors, without his Twitter bullhorn and fuming since his loss, Pence has been stepping up and fulfilling many of the ceremonial duties of the presidency.

On Thursday, Pence received a briefing at the Federal Emergency Management Agency headquarters in Washington from the FBI and other agencies on inauguration security and stopped by to thank White House phone operators, giving them a framed letter of appreciation. Later, he greeted members of the National Guard now protecting the Capitol building from further attack.

This weekend, he will travel to thank the troops — first flying to Lemoore, California, to deliver remarks to sailors, and then to Fort Drum, New York, to speak before 10th Mountain Division soldiers, many of whom recently returned from Afghanistan.

Pence was also the one who coordinated with lawmakers and the D.C. National Guard while the Capitol was under siege and he was in hiding. And last Friday, he called the family of slain Capitol Police officer Brian Sicknick, who died from injuries in the attack.

Pence's call to his successor is a continuation of the traditional show of comity between outgoing and incoming leaders that Trump has flouted. In 2008, then-Vice President Dick Cheney called Biden to congratulate him the night of his win and invited Biden and his wife, Jill, to tour the vice presidential residence on the grounds of the U.S. Naval Observatory shortly before the 2009 inauguration.

And in November 2016, Biden, Pence and their spouses met for lunch at the Naval Observatory after an earlier meeting at the White House.

“I told Mike, the vice president-elect, that I'm available to him 24/7,” Biden said after the get-together. “I plan on being available to Mike as senior staff for him as he moves.”

It's unclear whether Pence will do the same for Harris. Pence and his wife will be traveling over the weekend. And much of Washington is under heightened security after last week's violent insurrection at the Capitol, with law enforcement officials warning of more potential for violence surrounding Biden's inauguration.

While Biden said last week that he welcomed Trump's decision to skip his inauguration, he said he would be “honored” to have Pence attend.

“I think it’s important,” he said, that, as much as possible, “the historical precedents" with respect to the peaceful transfer of power “be maintained."