U.S. President Joe Biden mistakenly referred to British Prime Minister Rishi Sunak as "Mr. President."

The U.S. President swiftly corrected himself, joking that he had "promoted" Sunak.

The 80-year-old, seated across from Sunak for the bilateral meeting, said: "Well, Mr. President – Mr. President, I just promoted you. Mr Prime Minister, it’s great to have you back.

Sunak, who appeared to laugh off the error, has not been to the White House before as prime minister, only taking office last October.

Biden told him: "In the past few months, we have met each other in San Diego, and then we met in Belfast and we met in Hiroshima."

"And now we’re here; we’re going solve all the problems of the world in the next 20 minutes."

This is not the first time the U.S. president has recently appeared to fumble his words.

In April, during his visit to the Republic of Ireland, Biden appeared to confuse the New Zealand All Blacks rugby team name with the Black and Tans – a controversial War of Independence-era police force in Ireland.

And while he praised the strength of the U.K.-U.S. relationship on Thursday, saying it was in "really good shape," he has not always been so diplomatic.

Last month, he claimed he visited the island of Ireland to ensure the "Brits didn’t screw around" amid ongoing concern over the peace process and the impact of Brexit.