BEIRUT — With President Donald Trump poised to do what no other president has been willing to do — move the U.S. Embassy in Israel to Jerusalem — leaders and analysts in the region warned Tuesday it could spur insecurity and instability in a part of the world already beset by both.

Fulfilling an oft-repeated campaign pledge, Trump was to declare Jerusalem the capital of Israel in a speech at the White House today, three senior administration officials said. At the same time, he will set in motion a multiyear process for moving the embassy from Tel Aviv to Jerusalem, the officials said.

The president laid the groundwork in a series of phone calls Tuesday to Saudi Arabia's King Salman, Jordan's King Abdullah II, Palestinian Authority President Mahmoud Abbas and Egyptian President Abdel-Fattah el-Sissi.

All the leaders issued strongly worded declarations opposing the idea, which they fear could stir violent passions in a city that long has been a nationalist and religious tinderbox.

Jerusalem was a divided city until 1967, when Israel captured the eastern half of the city in a war with its Arab neighbors. Palestinians never have accepted Israeli rule over the entire city and have insisted East Jerusalem become the capital of any future Palestinian state, making decisions about its status especially fraught. Israelis always have considered Jerusalem their "eternal" capital.

Even before the president unveiled his plan, the emerging outline was enough to send a sense of anger and apprehension coursing through the Arab world and beyond.

European allies appealed anew for moderation on such a sensitive matter, and United Nations Secretary-General Antonio Guterres said through a spokesman that the city's status always had been regarded by the world body as a question that "must be resolved through direct negotiations."

In Israel, security forces braced for a potential eruption of unrest, according to Israeli news reports. The government of Prime Minister Benjamin Netanyahu stayed largely silent in the run-up to Trump's speech, seemingly worried any display of satisfaction over an explicit American endorsement of its long-held position might generate even more of a backlash from Arab neighbors.

"Trump's expected declaration on Jerusalem could turn into a match that would ignite a major fire in the violent region we are living in," veteran Israeli commentator Shimon Shiffer wrote in the Yediot Aharonot newspaper this week. The U.S. president, he said, "is handling every diplomatic issue like a pyromaniac who forces the people around him to put out the fire."

The eve of the president's statement saw the strongest public warning yet from Saudi Arabia, a key U.S. ally that has been seen by the White House as a potential partner in any overarching Mideast peace accord.

Jared Kushner, the president's son-in-law, has cultivated a close relationship with the young crown prince, Mohammed bin Salman, who is considered the main power behind the throne, and the Trump administration has cast Saudi Arabia as a key interlocutor in efforts to revive the peace process.

But the Saudi response to Trump's call — at least publicly — was harsh. King Salman declared any unilateral U.S. declaration on the status of Jerusalem would be a "dangerous step" and a "flagrant provocation of Muslims all over the world," according to a statement carried by the official Saudi Press Agency.

Trump's posture on Jerusalem drew expressions of bewilderment from some longtime watchers of the region, who pointed to a plethora of pitfalls awaiting, without the promise of achieving any particular policy aim.

"I'm just baffled," said Thomas Lippman, an expert in Arab affairs and U.S.-Saudi relations at the Middle East Institute in Washington. "Look at this from the Saudi perspective: They see themselves as leading the worldwide struggle with Iran. You don't win the battle for Muslim hearts and minds by being seen as soft on Israel."

But rhetorical flights do not always reflect leaders' true sentiments, particularly when it comes to Mideast peacemaking. Some observers suggested Trump could mollify Arab states if his announcement is framed in such a way that makes clear the United States still backs a negotiated solution to the two sides' competing claims to Jerusalem.

"It's not too late for Trump to make (today's) Jerusalem announcement artfully," former U.S. envoy to Israel Daniel Shapiro wrote on Twitter. But, he added, "it's been awfully clumsy getting to this point."

The U.S. Embassy won't be moved immediately, the administration officials said. In the meantime, Trump will sign a waiver to the 1995 law that demanded the State Department move the embassy by May 31, 1999.

Trump will not set a timetable, but one senior U.S. official said opening a new U.S. embassy in another country routinely takes three to four years.

"We don't just put a plaque on the door and open a mission," the official said. "There are major security and structural considerations and very, very strict guidelines anywhere in the world that have to be followed before a flag goes up," the official said.

Trump will have to continue to sign such waivers every six months to avoid cuts to the State Department budget that would kick in under the 1995 law. With Trump committing to building the embassy in Jerusalem eventually, the White House would like Congress to amend the law to eliminate the waiver requirement.

Palestinians long have considered Trump to be too partial toward Israel to be a fair broker in any peace process, and the latest developments brought new expressions of angst. A spokesman for Abbas, Nabil Abu Rudaineh, was quoted by the official Palestinian news agency WAFA as saying Abbas told Trump during their phone call that moving the embassy would have highly negative repercussions.

Abbas "warned of the dangerous consequences such a decision would have to the peace process and to the peace, security and stability of the region and of the world," his spokesman said.

More than any other issue associated with the conflict, the status of Jerusalem is a consistent flashpoint. A disputed holy site in its walled Old City — known to Jews as the Temple Mount and Muslims as the Noble Sanctuary — has been at the heart of many outbreaks of violence, including tension that boiled over into deadly clashes this year.

Palestinians have threatened to cut off contacts with Washington if Trump makes unilateral decisions about Jerusalem's status. The U.S. Consulate in Jerusalem, citing widespread calls by Palestinians for demonstrations in coming days, forbade U.S. government workers and their families from making personal trips to the Old City or the West Bank. It also advised U.S. citizens to exercise caution.

The Jerusalem dispute puts Jordan's monarch in a particularly awkward spot because of his role as guardian of Islam's third-holiest shrine, in the heart of the walled Old City. Although Israel has security control of the site, Abdullah wields religious and administrative authority over the Al-Aqsa compound, the raised plateau above the Western Wall, Judaism's holiest prayer site.

The senior U.S. officials insisted recognizing Jerusalem as the capital doesn't change U.S. positions on the administration of the Temple Mount and the borders of Israel and Palestine that might be part of a peace deal.

"The president believes this is a recognition of reality," the official said, in that the leadership of the state of Israel has run the country from Jerusalem for decades.

Jordan is one of only two Arab states — the other is Egypt — to have a peace treaty with Israel, and any struggle over the shrine's status generally leads to calls to abrogate the peace accord. The country's large Palestinian population is also sympathetic to the plight of kin in the West Bank, the Gaza Strip and East Jerusalem.

In a statement carried by Jordan's Petra news agency after the phone call with Trump, Abdullah said moving the U.S. Embassy to Jerusalem "will undermine efforts to resume the peace process and will provoke Muslims and Christians alike."

After Trump's phone conversation with Egypt's president, el-Sissi warned against "complicating the situation in the region by introducing measures that would undermine chances for peace," according to a communique cited by Egyptian state media.

The gathering storm over Jerusalem brought a flurry of diplomatic activity.

In a phone call with Secretary of State Rex Tillerson late Sunday, Jordan's foreign minister, Ayman Safadi, urged the United States to refrain from taking any steps aimed at altering the status quo on Jerusalem. Such moves would "trigger anger across the Arab and Muslim world, fuel tension and jeopardize peace efforts," Petra quoted Safadi as saying.

The Arab League Council called an emergency session in Cairo and issued a resolution saying that recognizing Jerusalem as the Israeli capital or establishing an embassy in the city would be a "blatant assault" on Arab nations as well as Muslim and Christian Palestinians.