King Charles III visit live updates: Charles, Camilla to visit Virginia on final day of trip

King Charles emphasized the importance of the NATO alliance as he spoke about how the U.K. answered the call after the terror attacks against the U.S. on Sept. 11, 2001.

"Today, Mr. Speaker, that same unyielding resolve is needed for the defense of Ukraine and her most courageous people," Charles said. "It is needed in order to secure a truly just and lasting peace from the depths of the Atlantic to the disastrously melting icecaps of the Arctic."

"The commitment and expertise of the United States Armed Forces and its allies lie at the heart of NATO, pledged to each other's defense, protecting our citizens and interests, keeping North Americans and Europeans safe from our common adversaries," he said.

His comments come amid Trump's criticism of NATO after several allied countries refused to back the U.S. war in Iran.

It's something that we don't see often in a divided Congress: a packed chamber, full of laughter, unity and standing ovations.

The laughter in the chamber is echoing off the walls. The king has had to stop a few times to allow for more laughter and applause.

Democrats and Republicans are listening attentively -- more than they do with a president even from their own party.

-ABC News' Rachel Scott

King Charles, speaking on American independence, said the founding fathers brought with them some ideals rooted in British common law -- including the Magna Carta.

"The U.S. Supreme Court Historical Society has calculated that Magna Carta is cited in at least 160 Supreme Court cases since 1789, not least as the foundation of the principle that executive power is subject to checks and balances," he said.

The remark was met with loud applause from the chamber.

King Charles decried acts of violence as he briefly mentioned the shooting at the White House Correspondents' Association Dinner on Saturday night.

"We meet, too, in the aftermath of the incident not far from this great building that sought to harm the leadership of your nation and to foment wider fear and discord. Let me say with unshakable resolve, such acts of violence will never succeed," he said.