This warning to US President Trump by Turkey's President Erdogan was made in no uncertain terms and this could lead to the end of diplomatic relations with Israel.
Turkey's President Recep Tayyip Erdogan said on Tuesday that Ankara could go as far as breaking off diplomatic ties with Tel Aviv if the United States formally recognises Jerusalem as Israel's capital, a move he said would be a "red line" for Muslims.
"Mr Trump! Jerusalem is a red line for Muslims," Erdogan said in a televised speech to his governing party, warning that if such a move was taken Turkey would call a summit of the Organisation of Islamic Cooperation (OIC).
"We are warning the US once again. You cannot take this kind of step."
Erdogan also said Jerusalem is inviolable for Muslims, and ignoring that would have serious consequences.
On Monday, Turkish Deputy Prime Minister Bekir Bozdag also raised the issue, saying the formal US recognition of Jerusalem as the capital of Israel would be a catastrophe and could lead to new conflict in the Middle East.
Speaking to reporters after a cabinet meeting, Bozdag, who is also the government spokesman, said Jerusalem's status had been determined by international agreements and that preserving it was important for the peace of the region.
"The status of Jerusalem and Temple Mount have been determined by international agreements. It is important to preserve Jerusalem's status for the sake of protecting peace in the region," Bozdag said.
"If another step is taken and this step is lifted, this will be a major catastrophe."
Israel captured Arab East Jerusalem in the 1967 Middle East war. It later annexed it, declaring the whole of the city as its capital, a move not recognised internationally. Palestinians want Jerusalem as the capital of their future state.
On Sunday, US President Donald Trump's adviser and son-in-law Jared Kushner said the president had not yet made a decision on whether to formally recognise Jerusalem as Israel's capital, a move that would break with decades of US policy.
President Erdogan and Abbas in contact
Past US presidents have insisted that the status of Jerusalem – home to sites holy to the Jewish, Muslim and Christian religions – must be decided in negotiations.
On Saturday, Erdogan held a phone call with Palestinian President Mahmoud Abbas in which they discussed the status of Jerusalem, sources in Erdogan's office said.
The sources said Erdogan told Abbas that preserving the status of Jerusalem was important for all Muslim countries, adding that international laws and United Nations decisions should be followed on the issue.
Any move by the United States to recognise Jerusalem as Israel's capital would fuel extremism and violence, Arab League Secretary-General Ahmed Aboul Gheit said on Saturday.
A senior Jordanian source said on Sunday that Amman has begun consultations on convening an emergency meeting of the Arab League and the OIC before any declaration by Trump this week.