Trump is to publicly address the question of Jerusalem on Wednesday and US officials familiar with his planning said he would declare Jerusalem as Israel's capital, though he would not order the embassy move immediately. Calling it Israel's "undivided" capital would mark an even more dramatic step, effectively recognizing Israel's annexation of East Jerusalem. The organization said on Monday that Trump's possible recognition would constitute "naked aggression" against Muslims and Arabs.
Since Palestinians also consider Jerusalem their capital, any policy that appears to favor the Israelis' claim over the Palestinians' is extremely contentious.
In 1995, Congress passed a law requiring the American embassy to be relocated to Jerusalem.
"It is a practical impossibility to move the embassy tomorrow", one official said. The US Consulate in Jerusalem warned Americans to be wary of demonstrations after Palestinians called for "three days of rage" across the West Bank.
The Trump administration appears to have missed a statutory deadline to sign a new waiver keeping the U.S. Embassy in Israel in the city of Tel Aviv. Pence is scheduled to travel to Israel later this month.
The planned announcement does not change U.S. policy on specific borders, dimensions and other issues that are subject to final status negotiations, the official added.
Wednesday's announcement, in line with a Trump campaign pledge, appears certain to inflame the Arab world and undermine Middle East peace talks, as Palestinian and Arab leaders have warned.
The U.K. foreign secretary, Boris Johnson, said it was too soon to comment definitively on the expected U.S. move. He additionally threatened to cut Turkey's diplomatic ties with Israel. "We're going forward on the basis of a truth that is undeniable. All parties should avoid shaking the long-term foundations of solving the Palestinian issues, and avoid creating new divisions in the region". "Let's wait and see what the president says exactly, but we view the reports that we've heard with concern", he said. More recently, the city experienced a wave of Palestinian stabbings in late 2015 in part because of growing numbers of visits by Jewish nationalists to the Temple Mount, and last summer, the city again experienced weeks of unrest when Israel tried to install security cameras next to the Al Aqsa Mosque after a Palestinian gunman killed two Israeli police officers.
"Our Palestinian people everywhere will not allow this conspiracy to pass, and their options are open in defending their land and their sacred places", said Hamas chief Ismail Haniyeh. Lawyers have said there's some flexibility in the exact timing.
The political benefits for Trump are unclear.
While the Israeli government considers Jerusalem the country's capital, the U.S. and the international community at large recognize Tel Aviv as Israel's capital city. The U.S. has consular offices in Jerusalem, but it's unlikely that they would be suitable for a permanent embassy. It could cause violence, given the symbolism of certain addresses in the Middle East.