WASHINGTON (Reuters) - Turkish President Tayyip Erdogan postponed a White House meeting with President Joe Biden, a source familiar with the situation and a Turkish official said on Friday of a visit that had been tentatively planned for May 9.

A new date will soon be set, the Turkish official said, requesting anonymity. The source familiar with the matter, speaking on condition of anonymity, said it was unclear what prompted the postponement.

A U.S. official noted that the meeting between the NATO allies had never been officially announced.

Representatives for the White House and the U.S. State Department had no immediate comment. Erdogan's office also had no immediate comment on the postponement, reported earlier by Bloomberg.

The meeting would have been the first bilateral visit to Washington since 2019 when Erdogan met with then President Donald Trump, a Republican. He and Biden have met a few times at international summits and spoken by phone since the Democratic U.S. president took office in January 2021.

Ties between the U.S. and Turkey have been long strained by differences on a range of issues. While they have thawed since Ankara ratified Sweden's NATO membership bid earlier this year, tensions persist over Syria and Russia and the war in Gaza.

Erdogan visited neighboring Iraq this week. Last weekend, he met with Hamas leader Ismail Haniyeh in Istanbul, the first meeting between Erdogan and a Hamas delegation headed by Haniyeh since Israel began its military offensive in the Gaza Strip following Hamas' Oct. 7 attack.

(Reporting by Steve Holland and Jonathan Spicer; additional reporting by Jarrett Renshaw, Humeyra Pamuk and Paul Grant; writing by Susan Heavey; Editing by Doina Chiacu and Alistair Bell)