Turkey’s president has threatened to sever ties with Israel if the United States recognizes Jerusalem as the capital of the Jewish state. Recep Tayyip Erdogan warned President Donald Trump against following through with electoral pledges to move the American embassy to the contested city. “Mr. Trump, Jerusalem is the red line of Muslims,” Erdogan stated in a televised address today, saying Turkey would consider breaking off ties with Israel altogether.

The comments prompted swift reactions from Israeli leaders. Education Minister Naftali Bennett, a senior partner in Prime Minister Benjamin Netanyahu’s coalition government, said, “Erdogan does not miss an opportunity to attack Israel. Israel will advance its goals, including the recognition of united Jerusalem as the capital of the state of Israel. … It's better to have a united Jerusalem than Erdogan’s sympathy.”

The war of words is likely to escalate should Trump, as some administration officials have suggested, announce tomorrow that the United States is relocating its embassy in Tel Aviv to Jerusalem, which the Palestinians claim for their own.

France and the European Union have joined Muslim leaders in urging Trump to reconsider amid worries that the move could re-ignite a fresh orgy of violence in the Middle East and beyond. Bekir Bozdag, Turkey’s deputy prime minister, apparently shares those concerns, saying Trump’s actions would result in “a major catastrophe.” Presidential spokesman Ibrahim Kalin used more measured language on Twitter, saying that moving the American embassy to Jerusalem would be “a fatal mistake and go against international agreements, UN resolutions and historical facts. We hope the US administration will avoid this mistake.”