A rare meeting between Turkish President Recep Tayyip Erdogan and his US counterpart Joe Biden at the White House has been postponed, a Turkish official said Friday, amid tensions over the Gaza war.

The talks, previously scheduled for May 9, would be the first White House meeting between the two leaders, who last met on the sidelines of the NATO summit in Lithuania in July.

"The visit planned for May 9 was postponed because of a change in Erdogan's programme," the official told AFP, speaking on condition of anonymity.

"A new date will be decided" after an exchange between the two presidents, the official added.

Erdogan's planned visit was never officially announced by the Turkish presidency but a Turkish official told AFP in March that it would take place on May 9.

The NATO allies are seeking to rebuild ties strained over a number of disputes including Turkey's delayed approval of Sweden's accession to the NATO alliance.

"The postponement is a pretty big deal, since Erdogan has been trying -- for three years now -- to get invited to the White House to meet US President Biden," said Soner Cagaptay, director of the Turkish Program at The Washington Institute.

  'Unconditional support' -

 Erdogan's harsh criticism of Israel's devastating response to the October 7 attack by Hamas is also a thorn in bilateral ties.

He has often compared Israeli Prime Minister Benjamin Netanyahu to Adolf Hitler and accused the United States of sponsoring the "genocide" of Palestinians.

In an address in Istanbul on Friday, Erdogan called Netanyahu "the butcher of Gaza".

"Netanyahu, like villains before him, has etched his name in history with shame as the butcher of Gaza," he said while also criticising Washington for its "unconditional military and diplomatic support" to Israel.

Erdogan lashed out at the US Senate for passing an aid package that earmarks $13 billion for Israel.

Erdogan's AKP government announced export restrictions on Israel early this month, after the party suffered a historic defeat in the March 31 local elections, losing control of many cities.

"Not to upset Biden ahead of the visit, Erdogan had been holding off regarding harsher steps targeting Israel. Now, all bets are off," Cagaptay said.

Erdogan met in Istanbul this month with Hamas chief Ismail Haniyeh, who has been a frequent visitor.

Hamas -- designated a terrorist organisation by the United States, the European Union and Israel -- is a rival of the Fatah faction that rules the semi-autonomous Palestinian Authority in the occupied West Bank.

Erdogan on Friday reiterated his position, saying: "We cannot be among those who label Hamas as a terror organisation just because Israel and its Western supporters want it that way."

He said Ankara considers Hamas "brothers who defend their homeland against occupiers".

Erdogan met with Biden's predecessor Donald Trump in the Oval Office at the White House in 2019.