King Charles III and Queen Camilla continued their four-day state visit to the US on Tuesday with a lavish state banquet, an aircraft flyover at the White House, and a speech from the King to Congress.

The trip, which comes as the US approaches the 250th anniversary of its independence from Britain, is aimed at celebrating the strong relationship between the two countries.

During his address to the state dinner, Trump described the history and bond between the US and UK "a friendship unlike any other on Earth", as well as praising golfer Rory McIlory, who was in attendance.

Before entering the White House, the president praised the King's speech to Congress, saying he had made him "very jealous".

The King responded with his own speech, making jokes about White House renovations and Winston Churchill.

Earlier, the King had arrived in the House of Representatives chamber to applause from hundreds of onlookers, including top US officials.

He followed in the footsteps of his late mother, Queen Elizabeth II, who had addressed the chamber in 1991.

In his speech, the King said the destinies of the US and UK had been interlinked ever since America's independence.

"As Oscar Wilde said, 'We have really everything in common with America nowadays except, of course, language!'" the King joked to laughter from his audience.

King Charles promoted the importance of protecting the environment.

"As we look toward the next 250 years, we must also reflect on our shared responsibility to safeguard Nature, our most precious and irreplaceable asset," he said.

The statement received a standing ovation.

The King concluded with a message of unity:

"I pray with all my heart that our alliance will continue to defend our shared values, with our partners in Europe and the Commonwealth, and across the world, and that we ignore the clarion calls to become ever more inward-looking."

Earlier in the day, King Charles and President Trump held a closed-door meeting inside the Oval Office of the White House.

Senior British and American officials were also present during the meeting.

On Tuesday morning, the royals received a ceremonial welcome at the White House, where President Trump presented a military spectacle to the King and Queen, including gun salutes and bugles.

President Trump gave a speech in front of the White House, in which he joked it was a beautiful British day - an apparent reference to the rainy conditions, which drew laughter.

Trump said the King's speech to Congress later was "going to make everyone very envious of that beautiful accent".

"He's a very elegant man," Trump said, before describing "the noble spirit of the British" and discussing the UK and US's shared history.

Following Trump's remarks, the King, Queen, president and first lady walked up the steps to the balcony overlooking the White House South Lawn to observe a flyover and troops marching below.

The previous day, the Royals arrived in the US by plane at Joint Base Andrews, Maryland, to a waiting red carpet.

After walking through a guard of honour, a military band played both the US and UK national anthems.

The royal couple then went on to meet Donald and Melania Trump at the White House for afternoon tea.

The King and Queen attended a British embassy garden party, where the King chatted with former speaker of the House of Representatives Nancy Pelosi among other guests.

He tells US lawmakers his address comes the two nations' relationship is "more important" than ever "in times of great uncertainty".

There were some lines in the speech that may have buoyed Democrats โ€“ and raised eyebrows in the White House.

The US president was speaking about his mother Mary's love for the Royal Family during a speech at the White House, attended by the King and Queen.

King Charles will address the US Congress on Tuesday at a time of diplomatic tensions between London and Washington.

After landing, the royals were greeted by US President Donald Trump at the White House and later visited the British Embassy.