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.

King celebrates independence and focuses on repairing a frayed relationship

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.”

Trump hosted the royal couple for a jovial state dinner later Tuesday in the East Room of the White House. About 130 guests were seated at two long tables that were decorated with low floral arrangements. The guests included tech leaders such as outgoing Apple CEO Tim Cook and Amazon founder Jeff Bezos, along with conservative Supreme Court justices and several Fox News journalists and hosts.

Charles and Camilla will continue their U.S. tour this week with stops in New York City and Virginia.

During his roughly 20-minute speech to Congress, the king, who is expressly apolitical, never directly criticized Trump. Still, the contrast was apparent at times and some British commentators described his speech as more political than they had expected.

Just two months earlier, Trump stood at the same lectern and chided Democrats for not standing during part of his State of the Union address. The king, for his part, elicited multiple standing ovations from Democrats and Republicans who listened with rapt attention.

Charles is just the second British monarch to address a joint session of Congress. His mother, Queen Elizabeth II, delivered a similar speech in 1991 highlighting the historic ties between both countries and the importance of their democratic values.

Charles acknowledges a ‘more volatile and more dangerous’ world

While the king paid tribute to those remarks, he acknowledged that today’s environment is “more volatile and more dangerous than the world to which my late mother spoke.”

Many of the lawmakers in the room were at Saturday’s White House Correspondents’ Dinner, which was disrupted by a shooting that authorities have described as an attempted assassination against Trump.

“Let me say with unshakeable resolve,” Charles said. “Such acts of violence will never succeed.”

Meanwhile, Trump’s up-and-down relationship with British Prime Minister Keir Starmer has taken a particularly sour turn over the past several months as the Republican president has sought to rally international support for the war in Iran. Trump criticized Starmer, who has largely resisted his overtures, by saying, “This is not Winston Churchill that we’re dealing with.”

Trump has also imposed tariffs on the U.K. and warned of additional levies despite a Supreme Court ruling earlier this year that has made such unilateral moves more challenging. Trump threatened just last week to slap a “big tariff” on the U.K. if it doesn’t scrap a digital services tax on U.S. technology companies.

Trump has more broadly challenged the traditional trans-Atlantic alliance with efforts to annex Greenland and threats to walk away from NATO. He has repeatedly imposed tariffs on and taunted Canada, a member of the British Commonwealth.

Ahead of his speech, the king had faced some calls on Capitol Hill to meet with Epstein’s victims while he is in the U.S. He didn’t make a direct mention of the convicted sex offender, but did reference the “collective strength” in the U.S. and the U.K. to “support victims of some of the ills that, so tragically, exist in both our societies today.”

If Charles offered low-key criticism of Trump, the president didn’t seem to mind. He said later that the king “made a great speech.”

“I was very jealous,” he said.