Britain's King Charles III toasts with President Donald Trump during a State Dinner in the East Room of the White House State Dinner Tuesday, April 28, 2026, in Washington. Photo: AP/Alex Brandon

Britain's King Charles III hailed his country's longstanding relationship with the United States as he attended a lavish state dinner at the White House on Tuesday during a four-day visit to mark the 250th anniversary of US independence.

Echoing the tone of an earlier speech to Congress, King Charles III highlighted the historical and cultural ties that he said have cemented an enduring bond between the US and the UK, calling it “one of the most consequential alliances in human history”.

As he spoke in unifying, optimistic terms, he delivered a series of nuanced warnings encouraging leaders in the US to remain collaborative and engaged in global affairs while also urging “that we ignore the clarion calls to become ever more inward-looking" as the relationship is tested by the Iran war.

In just the second speech to Congress by a British monarch following Elizabeth II in 1991, Charles also pointed to shared democratic traditions.

The visit comes at a delicate moment, with US President Donald Trump criticising the UK over its stance on Iran and other policies.

Trump has repeatedly criticised British Prime Minister Keir Starmer over his opposition to the Iran war, and there is no indication that King Charles III has shown support for the US leader's stance.

In his toast, King Charles III said he was "here to renew an indispensable alliance which has long been a cornerstone of prosperity and security."

The British monarch pointedly mentioned the importance of international alliances like NATO that Trump has repeatedly questioned, and called for continued support for Ukraine amid Russia's ongoing full-scale invasion.

"Together, we can meet the challenges of an increasingly complex and contested world," he added.