Russia-Ukraine updates: 2 US veterans who joined Ukrainian forces missing

President Joe Biden met with the leaders of Sweden and Finland at the White House Thursday after the two countries submitted applications to join NATO.

"Today I'm proud to welcome and offer the strong support of the United States for the applications of two great democracies, and two close, highly capable partners to join the strongest, most powerful defensive alliance in the history of the world," Biden said.

Biden reaffirmed the U.S.'s support for the Nordic countries' applications to join the alliance.

"Finland and Sweden make NATO stronger not just because of their capacity, but because of their strong democracies and a strong united NATO is the foundation of America's security," he said.

Biden also sent a message to Russian President Vladimir Putin and Russia.

"So let me be clear: New members joining NATO is not a threat to any nation. It never has been. NATO's purpose is to defend against aggression, that's its purpose, to defend," Biden said.

-ABC News' Karen Travers and Justin Gomez

Vadim Shishmarin, 21, is back in court, one day after he pleading guilty to killing a 62-year-old Ukrainian civilian just days into the conflict.

Shishmarin confessed to the killing Thursday morning.

The widow of the victim testified in court that her husband meant everything to her, and she thinks the Russian soldier deserves life in prison, but if he gets exchanged for any of the Azovstal defenders she wouldn’t object.

"I feel very sorry for him," she said. "But for a crime like that -- I can't forgive him."

Shishimarin could spend the rest of his life in prison.

-ABC News' Joe Simonetti

Mass shelling of the Sumy region continued from Russian territory Wednesday evening, said Dmytro Zhyvytskyy, the governor of Sumy, on Telegram.

The shelling was along the entire border between the Sumy region and Russia, according to Zhyvytskyy.

Zhyvytskyy said Ukraine responded to the shelling appropriately and no casualties were reported.

-ABC News' Joe Simonetti

Mykhaylo Podolyak, an adviser to Ukrainian President Volodymyr Zelenskyy, told Russia not to offer Ukraine a cease-fire, because it would be impossible without Russian troops' withdrawal.

"Ukraine is not interested in new 'Minsk' and the war renewal in a few years," Podolyak said in a tweet, referring to the capital of Belarus and that country's allegiance to Russia. "Until [Russia] is ready to fully liberate occupied territories, our negotiating team is weapons, sanctions and money."

-ABC News' Joe Simonetti