Turkish President Recep Tayyip Erdogan warned his United States counterpart Donald Trump on Tuesday against a possible recognition of Jerusalem as the Israeli capital while Saudi Arabia expressed “grave and deep concern”.

“Mr Trump! Jerusalem is a red line for Muslims,” Erdogan said in a televised speech to his ruling party, warning that if such a move was taken Turkey would call a summit of the Organisation of Islamic Cooperation (OIC) and could even “go as far as” cutting its ties with the Jewish state.

US President Donald Trump faces a key decision this week over Jerusalem's status, potentially reversing years of US policy and prompting a furious response from the Palestinians and the Arab world.

Meanwhile the official Saudi Press Agency, citing a foreign ministry source said: “Saudi Arabia (expresses) grave and deep concern over reports that the US administration intends to recognise Jerusalem as the capital of Israel, and to relocate its embassy to Jerusalem.”

“This step will have serious implications and will further complicate the Palestinian-Israeli conflict. It will also obstruct the ongoing efforts to revive the peace process.” The status of Jerusalem is one of the most contentious issues of the long-running Israeli-Palestinian conflict.

Facing dark warnings of a historic misstep and widespread unrest, Trump on Monday delayed a decision on whether to recognise Jerusalem as the Israeli capital and move the US embassy there.

The White House said Trump would miss a deadline to decide on shifting the embassy from Tel Aviv, after a frantic 48 hours of public warnings from allies and private phone calls between world leaders.

The mercurial president has yet to make his final decision, officials said, but is expected to stop short of moving the embassy to Jerusalem outright, a central campaign pledge which has been postponed once already by the new administration.

EU warns of serious repercussions

The European Union also warned of possible “serious repercussions” if US President Donald Trump decides to recognise Jerusalem as the Israeli capital and move the US embassy there.

The EU, which supports a two-state solution to the conflict, warned against doing anything that would jeopardise the peace process.

“Since early this year, the European Union was clear in its expectation that there can be reflection on the consequences that any decision or unilateral action affecting Jerusalem's status could have,” EU diplomatic chief Federica Mogherini's office said in a statement.

“It might have serious repercussions on public opinion in large parts of the world,” it added. “The focus should therefore remain on the efforts to restart the peace process and avoiding any action that would undermine such efforts.”

Trump has yet to make his final decision, US officials have said, but he is now expected to stop short of moving the embassy to Jerusalem — though he may still recognise the city as Israel's capital.

Both Israelis and Palestinians claim Jerusalem as their capital and previous peace plans have stumbled over debates on whether, and how, to divide sovereignty or oversee holy sites.

The 28-nation EU said it would “continue to engage with both parties and its international and regional partners” to support a resumption of a meaningful peace process.