Britain's King Charles will visit the U.S. starting on Monday to mark America's 250th anniversary – his first trip since his coronation nearly three years ago.

Buckingham Palace has said the visit "will celebrate the historic connections and the modern bilateral relationship between the United Kingdom and the United States." But it comes at a time when the normally close relationship between the U.S. and Europe is strained.

For decades, the U.S. and the U.K. have enjoyed what Winston Churchill called a "special relationship." President Trump visited the U.K. in September – enjoying a carriage ride with the king, an inspection of troops and a state banquet.

Recently though, Mr. Trump caused offense in the U.K. by criticizing British Prime Minister Keir Starmer for his response to the Iran war. 

Mr. Trump also dismissed the U.K.'s two aircraft carriers as "toys." 

King Charles is a constitutional monarch with no power to decide British government policy. But the royals, with their pomp and circumstance, bring a special kind of diplomatic firepower, and the king will no doubt do his best to navigate the currents in the relationship, and quell the troubled waters.

But there are also risks for Charles in visiting. Some U.S. lawmakers are demanding that his brother Andrew Mountbatten-Windsor, formerly known as Prince Andrew, testify before Congress about his friendship with Jeffrey Epstein, which could be a source of embarrassment for the king in Washington.

Mr. Trump said late last month that Charles and Queen Camilla will visit the U.S. from Monday to Thursday. 

Charles is expected to address a joint meeting of Congress and attend a beautiful banquet dinner at the White House. Charles and Camilla are also scheduled to visit New York City.