U.S. President Donald Trump offered his "heartfelt appreciation" to Emperor Akihito and Empress Michiko on Monday ahead of the emperor's abdication and the beginning of the country's new era.

"As the Heisei era draws to a close and a new generation prepares to ascend the throne, I want to recognize the tremendous importance that the United States attaches to its close relationship with Japan," Trump said in a statement.

He noted that the outgoing emperor, to be succeeded by Crown Prince Naruhito on Wednesday, has welcomed five U.S. presidents to Japan, including Trump in November 2017, during his reign "from the end of the Cold War to the present day."