King Charles has sent his "warmest congratulations" to the United States as the country celebrates 250 years since the Declaration of Independence.
In a messages addressed to President Donald Trump, the King said 2026 marked a "truly historic milestone and a moment of great celebration for Americans everywhere".
He praised the UK's relationship with the US as one of "extraordinary evolution" and called the celebration "an opportunity to pause and reflect on the remarkable journey" of the US over the past 250 years.
"The connection between our people is one that I trust will only grow stronger with time," he added.
In his message, the King said the US and UK had overcome conflict to forge "one of the closest and most productive alliances the world has seen".
"Through centuries of shared challenge and achievement, our nations have built a relationship founded on friendship, trust and a belief in liberty, the rule of law and the dignity of all people."
This "unique and far-reaching" alliance, he said, spans defence and security, trade and investment, science, research, education, culture and the arts.
The King praised the "enduring bond between our countries", which he said he had seen "first-hand" during his state visit to Washington DC in May.
He also said he held a "deep appreciation of our shared responsibility to protect the natural world", decisions about which would determine both countries' prosperity and national security for future generations.
The Declaration of Independence, signed in 1776, established the United States of America's independence from the colonial rule of Great Britain - its anniversary is celebrated on 4 July.
Trump is set to attend celebrations in Washington DC on Saturday, including flyovers by hundreds of aircraft and a fireworks display.
The Fourth of July fireworks display is an annual tradition in Washington DC and Trump has promised that this year's version - which is scheduled to begin after his remarks - would be the "largest fireworks show in history".
Festivities are also taking place in other parts of the US.
The Times Square Ball in New York will drop eight times to signal midnight in every US time zone.
In Philadelphia, where the Declaration of Independence was signed in Independence Hall 250 years ago, there will be a celebration concert featuring stars including Christina Aguilera.
In May, the King and Queen Camilla visited the US for the first British state visit to the country since Queen Elizabeth II's visit in 2007.
The royals travelled against a backdrop of political tension after the UK government decided not to get involved in the Iran war.
In a speech to US Congress, the King urged US lawmakers to defend Ukraine and support Nato.
A senior royal aide said of the pair's relationship during the trip: "They get on very well... It's a pairing, sort of unlikely though it might be in many ways…"
"I mean, given some of the issues that have presented themselves in the bilateral relationship, you'd think it might all be a bit tricky."
And Trump's review seemed clear: "The greatest king in my book."
