Turkish President Recep Tayyip Erdogan has urged leaders of Muslim nations to recognise Jerusalem as the “occupied capital of the Palestinian state”.
Addressing a summit of the Organisation for Islamic Co-operation, he said the US decision to recognise the city as Israel’s capital was “null and void”.
Mr Erdogan also again accused Israel of being a “state of terror”.
Palestinian leader Mahmoud Abbas said the US had “disqualified itself from playing a role in the peace process”.
“We shall not accept any role for the United States in the peace process. They have proven their full bias in favour of Israel,” he told the summit.
The status of Jerusalem goes to the heart of Israel’s conflict with the Palestinians.
The city is home to key religious sites sacred to Judaism, Islam and Christianity, especially in East Jerusalem.
Israel occupied the sector, previously occupied by Jordan, in the 1967 Middle East war and regards the entire city as its indivisible capital.
The Palestinians claim East Jerusalem as the capital of a future state, and its final status is meant to be discussed in the latter stages of peace talks.
Israeli sovereignty over Jerusalem has never been recognised internationally, and all countries currently maintain their embassies in Tel Aviv. However, President Donald Trump has announced that the US will eventually move its embassy.
The BBC’s Mark Lowen in Istanbul says the rhetoric at the start of the OIC summit was strong.
But the question is what in practice the grouping can do, he adds, given the fact some members are more pro-Trump than others.
Our correspondent says various countries have only sent ministers to the meeting, possibly a sign of low expectation, and the reaction on the streets of the Muslim world to the Jerusalem issue has been relatively restrained.
Mr Erdogan threatened to cut Turkish ties with Israel before Mr Trump’s announcement last week, though he made no mention of this in his speech.
Turkey and Israel only restored diplomatic relations in 2016, six years after Turkey severed ties in protest at the killing of nine pro-Palestinian Turkish activists in clashes with Israeli commandos on board a ship trying to break Israel’s naval blockade of Gaza.
Mr Erdogan instead urged a unified response by Muslim nations to Mr Trump’s Jerusalem decision.
“I invite all the countries that value international law and justice to recognise Jerusalem as the occupied capital of the Palestinian state,” he said.
“Those who fight with their friends forget to fight with their enemies,” he added. “We need a diplomatic solution. We have to stop Israel gaining more land from Palestine day by day. And we must not accept the policies and attitude Israel has been displaying day by day.”