The Organisation of Islamic Cooperation on Monday called for a summit of Muslim nations if the United States takes the controversial decision to recognise Jerusalem as Israel's capital.
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.
The 57-member OIC sought to amplify concern over the possible move in an emergency meeting on Monday in the Saudi Red Sea city of Jeddah.
"If the United States takes the step of recognising Jerusalem as the so-called capital of Israel, we unanimously recommend holding a meeting at the level of council of foreign ministers followed by an Islamic summit as soon as possible," the pan-Islamic body said in a statement.
The OIC also warned that recognising Jerusalem or establishing any diplomatic mission in the disputed city would be seen as a "blatant attack on the Arab and Islamic nations".
The status of Jerusalem is one of the most contentious issues of the long-running Israeli-Palestinian conflict.
Most of the international community, including the United States, does not formally recognise Jerusalem as Israel's capital, insisting the issue can only be resolved through final-status negotiations.
Central to the issue of recognition is the question of whether Trump decides to move the US embassy in Israel to Jerusalem.
All foreign embassies are located in Tel Aviv with consular representation in Jerusalem.
Israelis and Palestinians are eagerly watching to see whether he again renews a waiver delaying the move, as his predecessors have done.
There are suggestions that Trump will sign the waiver and decline to move the embassy for now, but later this week declare Jerusalem as Israel's capital.
Israel, which seized the largely Arab eastern sector of Jerusalem during the 1967 Six-Day War and later annexed it, claims both halves of the city as its "eternal and undivided capital".
But the Palestinians want the eastern sector as capital of their promised state and fiercely oppose any Israeli attempt to extend sovereignty there.
Several peace plans have come unstuck over debates on whether, and how, to divide sovereignty or oversee the city's sites holy to Christians, Jews and Muslims.
