President Donald Trump, a real estate tycoon and author of The Art of the Deal, fancies himself a dealmaker. Indeed, since taking office he has projected himself as being able to broker the ultimate deal: an Israeli-Palestinian peace agreement. But in announcing on Dec. 6 that he would recognize Jerusalem as Israel’s capital and move the U.S. embassy there, he threatens to destroy any remaining hope of resuscitating the moribund peace talks.

Palestinian President Mahmoud Abbas and Jordan’s King Abdullah II have warned against the move. Even the Saudi government, itself heavily involved in disrupting the politics of the region, defended the rights of the Palestinians to share the city as their capital; and Turkey threatened to break relations with Israel in the event the United States took the move. Pope Francis has warned that the move could add a new source of tension “in a world already shaken and scarred by many cruel conflicts.”

The international community has long recognized the unique political and religious status of Jerusalem. The 1947 U.N. Partition Plan for Palestine envisaged a special status for the holy city as a corpus separatum under international governance. The Israeli War of Independence left the city divided along the famous green line between Israel and Jordan.

If Mr. Trump goes through with his announced intentions, he will dispel any thought that he can broker an agreement in the disputatious Holy Land.

After the Six-Day War in 1967, Israel gained control of the whole city, but the international community has never recognized Israeli sovereignty over Jerusalem; and for that reason, nearly all foreign embassies are located in Tel Aviv. But when the Holy See extended diplomatic recognition to Israel in 1994, it opened an office in Tel Aviv as its “embassy.” Interestingly, the apostolic delegate to Jerusalem and Palestine, Leopoldo Girelli, resides in Arab East Jerusalem.

When Israel and the Palestine Liberation Organization signed the Oslo Accords in 1993, the status of Jerusalem was left to be discussed in “final status talks.” Those talks were originally scheduled for 1996, but they did not begun until 1999 and the topic was ultimately left to the Camp David II talks in 2000, hosted by Bill Clinton. The future of Jerusalem was one of the issues over which final status talks collapsed, as Palestinian leader Yasser Arafat could not agree to a resolution without the approval of the kings of Jordan, Morocco and Saudi Arabia, descendants of the prophet Mohammed who hold a hereditary responsibility for the Muslim holy places there.

There was also great consternation over a tentative agreement to hand over the Christian Armenian Quarter of the Old City to Israel. The Christian patriarchs and heads of churches protested that agreement, even though Israelis had already bought up much of the property in that district.

Declaring Jerusalem as Israel’s “united and eternal capital,” as Israeli leaders put it, is a serious step, signaling diplomatic approval for Israel’s seizure of the city by force and eroding what had been united international opposition to the idea that the Holy City could be claimed through Israel’s military victory. Furthermore, Israel’s physical control of the city has been accompanied by the seizure of Palestinian homes and whole Palestinian neighborhoods by ultra-Zionist settlers.

In quiet acts of ethnic cleansing, Palestinian Jerusalemites are denied residency because of extended absences or because they have married residents of the West Bank. Their neighborhoods are rezoned for public uses; their homes are occupied by Jewish settlers and they have no legal recourse. Moving the U.S. embassy to Jerusalem means giving the seal of approval to “facts on the ground” that despoil Palestinian Jerusalemites of their birthright.

With today’s announcement, Mr. Trump has dispelled any thought that he can broker an agreement in the disputatious Holy Land. Palestinians will put no trust in him, and they will be right to believe the United States has given up all pretense to being an honest broker of an Israeli-Palestinian peace.

The Middle East is already a tinderbox. Besides continuing to support Sunni insurgents in Syria and Iraq, Saudi Arabia is mired in a religious war with the Yemeni Houthi, whom they believe are heretics and on whom they have tried to impose their own harsh Wahhabism, an ultra-conservative understanding of the Muslim faith; they have also tried to strangle the pluralist monarchy in Qatar and remove the Sunni premier of multiconfessional Lebanon.

With ISIS on the run, there is little evidence that the Iraqi government will come to agreement with the Kurds, the Sunni or other minorities to function as a single country with a common future. Alas, after more than six years of civil war, Syria has been laid utterly to waste. The Middle East is a region near the tipping point. A provocative decision on Jerusalem could be all it takes to send the region spinning into cataclysm.

One wonders where the president is getting his advice. Certainly not from General H. R. McMaster, the national security adviser, who, insiders say, cleaned out an Israeli clique in his shop, a legacy from the disgraced General Michael Flynn. Could it be from Steve Bannon, his former adviser, who delights in stirring up trouble? Even with all his Russian baggage, I doubt it was Jared Kushner, who had too much riding on his personal involvement in a peace settlement to cross the bright red line around Jerusalem.

Perhaps it was his new ambassador to Israel, David Friedman, a backer of the Israeli settler movement and an opponent of the two-state solution. Breaking with the international consensus and more than a quarter-century of bipartisan U.S. policy would seem to be right in line with his beliefs. It would also serve the ideological agenda of his friend, Israeli Premier Bibi Netanyahu, for occupying all of “Judea and Samaria,” or what the world thinks of as Jerusalem and the West Bank.

By following through with his promises on Jerusalem, not just the West Bank but the Arab Street across the Middle East is liable to rise up in protest. Jerusalem is sacred to Muslims as well as Jews and Christians. Dealing the Jerusalem card to Israel is a prescription for chaos, opening a Pandora’s box of unforeseen ills to menace the rest of the world.

It could make the rolling disaster in Iraq look like the good old days.

This article has been updated.

Drew Christiansen, S.J., served as the editor in chief of America from 2005 to 2012. He was a Distinguished Professor of Ethics and Human Development at Georgetown University and a senior fellow with the Berkley Center for Religion, Peace and World Affairs. He was co-editor with Carole Sargent of A World Free from Nuclear Weapons: The Vatican Conference on Disarmament (Georgetown, 2020).