Biden tells Americans freed from Russian detention, 'Welcome almost home'

President Joe Biden on Thursday celebrated an extraordinary prisoner exchange that freed several Americans wrongfully detained in Russia, calling it a "feat of diplomacy and friendship" in remarks from the White House.

Biden was surrounded by family members of Evan Gershkovich, Paul Whelan, Alsu Kurmasheva and Vladimir Kara-Murza as he spoke about the efforts involved in the swap, which is the largest since the Cold War involving 24 people and several countries.

"This is an incredible relief for all the family members gathered here," Biden said. "It's a relief to the friends and colleagues all across the country, who've been praying for this day for a long time."

Biden took a moment to describe the three American citizens and one legal permanent U.S. resident being brought back to the U.S. He said each was arrested, convicted and sentenced by Russian authorities "with absolutely no legitimate reason whatsoever."

"And now their brutal ordeal is over and they're free," Biden said.

Biden, who officials said was directly involved in helping negotiate the deal, had gathered the families at the White House earlier Thursday to inform them that the release was underway. Biden said he and the families were able to contact the freed Americans over the phone.

When asked what he said to them, Biden replied: "I said, 'Welcome almost home.'"

The multipart prisoner swap is the product of months of detailed, painstaking negotiations, according to national security adviser Jake Sullivan. The nations involved also included Germany, Poland, Slovenia, Norway and Turkey.

A senior administration official said even the day Biden announced he was no longer seeking a second term, he was on the phone working to secure this deal.

Sullivan, who addressed reporters at the White House daily briefing, choked back tears as he emotionally talked about the extensive effort to secure the deal and said it "was vintage Joe Biden rallying American rallying American allies to save American citizens."

Biden, in his remarks, touted his administration's work and the power of global alliances while also seemingly criticizing his Oval Office predecessor Donald Trump.

"For anyone who questions whether allies matter, they do. They matter," he said.

"Our work did not start just on Day 1. It started before Day 1," Biden said. "During the transition, I instructed our national security team to dig into all the cases of hostages being wrongfully detained, which were inherently -- well, we inherited them from the private -- the prior administration."

"I wanted to make sure we hit the ground running, and we did," Biden continued. "As of today, my administration has brought home over 70 Americans who were wrongfully detained and held hostage abroad. Many since before I took office."

Later, when asked by a reporter about Trump's repeated claims he could've gotten the hostages out of Russia without concessions, Biden took a more direct jab at his former political opponent.

"Why didn't he do it when he was president?" Biden responded.

Speaking further on Thursday's release, Biden noted several of the 16 individuals freed on Thursday were Russian political prisoners who "stood up for democracy and human rights" and were subsequently jailed by their own leaders. He took a moment to contrast that with the work of the U.S. and its partners.

"The United States helped secure their release as well. That's who we are in the United States," he said. "We stand for freedom, for liberty, for justice, not only for our own people, but for others as well. And that's why all Americans can take pride in what we've achieved today."

As he closed his remarks, Biden turned back to the families gathered in the State Dining Room, saying he couldn't imagine what they've endured these last few years.

He then led the singing of "Happy Birthday" to Miriam, the daughter of Kurmasheva, an American-Russian journalist who was freed on Thursday. Biden said Mariam will turn 13 on Friday and will now be able to celebrate with her mother.

"That's what this is all about. Families able to be together again, like they should have been all along," Biden said. "So, I want to thank you again to everyone who did their part. In just a few hours, we'll welcome home our fellow Americans."

The two top Republicans in Congress issued a joint statement calling the Gershkovich and Whelan release "encouraging news" but then went on to cite the "costs of hostage diplomacy."

"Without serious action to deter further hostage-taking by Russia, Iran, and other states hostile to the United States, the costs of hostage diplomacy will continue to rise. As we renew our call for the return of all persons wrongfully detained by the Kremlin, we recognize that trading hardened Russian criminals for innocent Americans does little to discourage Putin's reprehensible behavior," House Speaker Mike Johnson and Senate Minority Leader Mitch McConnell said.

ABC News' Lauren Peller contributed to this report.