Britain's King Charles III listens as President Donald Trump speaks during a State Visit arrival ceremony on the South Lawn of the White House, Tuesday, April 28, 2026, in Washington. (AP Photo/Alex Brandon)

WASHINGTON (AP) — King Charles III marked the 250th anniversary of American independence from Britain with gratitude that the two countries united to build “one of the most consequential alliances in human history” while urging “that we ignore the clarion calls to become ever more inward-looking.”

Speaking Tuesday to a joint session of the U.S. Congress, Charles repeatedly highlighted the historical and cultural ties that he said have cemented an enduring bond between the United States and the United Kingdom. But even as he spoke in unifying, optimistic terms, he delivered a series of nuanced warnings encouraging leaders in the U.S. to remain collaborative and engaged in global affairs.

He said the alliance between the U.S. and the U.K., tested anew by President Donald Trump’s war in Iran, “cannot rest on past achievements.” Charles urged “unyielding resolve” in backing Ukraine against Russia and heralded the NATO alliance that Trump has consistently undermined.

The king praised religious pluralism and interfaith dialogue in terms that are rare in Trump’s Washington. As the White House rolls back regulations aimed at denting climate change, the king encouraged those in power to “reflect on our shared responsibility to safeguard nature, our most precious and irreplaceable asset.”

At one point, Charles traced the notion of checks and balances on executive power to the Magna Carta, the foundational legal document sealed by King John in 1215. Trump told The New York Times earlier this year that he was constrained only by “my own morality.”

And acknowledging a scandal that has roiled politics in both the U.S. and U.K., Charles subtly alluded to the victims of Jeffrey Epstein, the convicted sex offender with ties to British officials, including the king’s brother, Andrew.

Charles is on a four-day visit to the U.S. intended to both celebrate American independence and to repair the country’s fraying relationship with the U.K. He hardly arrived in Washington as an oppositional figure to Trump. Joined by Queen Camilla, Charles had a warm greeting with the president and first lady Melania Trump at the White House earlier Tuesday.

In his welcome remarks, Trump also highlighted the shared history between the two countries.

“American patriots today can sing, ‘My country, ’tis of thee, sweet land of liberty,’ only because our colonial ancestors first sang, ‘God save the king,'” Trump said.

The leaders met privately in the Oval Office for a meeting Trump later described as “really good,” adding that Charles is a “fantastic person.”