WASHINGTON — King Charles III addressed a joint session of Congress on Tuesday, calling on Republican leaders to support Ukraine and to maintain commitment to NATO. The address served as the centerpiece of a four-day state visit by the king and Queen Camilla designed to underscore ties between Britain and its former colony over the 250 years since American independence.

Charles is the second British monarch to address Congress in a joint session, following his mother, Queen Elizabeth II, in 1991. The speech was scheduled to begin at 3 p.m. and last about 20 minutes, and was to be followed by a state dinner at the White House on Tuesday night.

The king said conflicts in Europe and the Middle East pose immense challenges for the international community and stressed the need to work together. "The challenges we face are too great for any one nation to bear alone," he said. He urged continued defense of shared values with partners in Europe, the Commonwealth, and across the world, and urged ignoring calls to become inward-looking.

He reminded Congress that NATO assisted the United States after the September 11, 2001, attacks and said the same resolve should be extended to Ukraine to secure a just and lasting peace. He also said climate action is key for prosperity and national security. A palace source said the king would say, "Time and again, our two countries have always found ways to come together."

"I served with immense pride in the Royal Navy, following in the Naval footsteps of my Father, Prince Philip, Duke of Edinburgh; my Grandfather, King George VI; my Great-Uncle, Lord Mountbatten; and my Great-Grandfather, King George V," Charles said. He called on Republican leaders to support Ukraine and maintain commitment to NATO, urging that the same resolve shown after the September 11 attacks be extended to securing a just and lasting peace.

President Donald Trump hosted the king and queen at the White House earlier on the day of their state visit but did not attend the speech due to security concerns. Speaking at the White House, Trump said, "Americans have had no closer friends than the British. We share the same language. And together, our warriors have defended the same extraordinary civilization under twin banners of red, white and blue." He also said, "Long before Americans had a nation or a Constitution, we first had a culture, a character and a creed."

The visit unfolded at a moment of strain in U.S.-British relations. Trump has repeatedly clashed with British Prime Minister Keir Starmer over the United States' war with Iran, derided the British government's refusal to commit its defense forces to the conflict, and mocked the Royal Navy's battleships as "toys." An internal Pentagon email suggested Washington could review its support for Britain's claim to the Falkland Islands. The Trump administration also criticized other NATO members for not offering more assistance to U.S. military operations against Iran and pressed European countries to share more of the financial burden for supporting Ukraine against Russia's invasion.

Security around the visit was heightened following a shooting at the White House Correspondents' Association dinner attended by Trump, several members of his Cabinet, and members of Congress. According to authorities, the alleged gunman was a California tutor targeting Trump administration officials based on rank. Law enforcement officers were stationed on the rooftop of the Capitol and patrolling surrounding areas before the king's arrival.