U.S. President Donald Trump will declare Wednesday that Jerusalem is the capital of Israel, senior U.S. officials said Tuesday, in a move that would upend Washington's long-standing policy on the Middle East and undermine efforts to promote peace talks between Israel and the Palestinians.

In a planned speech, Trump will direct the State Department to start the process of relocating the U.S. Embassy in Israel from Tel Aviv to Jerusalem, the administration officials told reporters.

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.

Trump does not have a specific time frame for moving the embassy. "This will be a matter of some years," one official said, citing the need for time to find an appropriate site and address security concerns and other logistical matters.

As such, the president will sign a national security waiver that would allow the administration to keep the embassy in Tel Aviv for an additional six months, according to the officials, speaking on condition of anonymity.

Despite what Palestinian and Arab leaders regard as a highly contentious step, one official said Trump remains firmly committed to the United States facilitating a peace deal between Israel and Palestinians, and he believes such a deal "is in reach and can be achieved."

Recognizing Jerusalem as Israel's capital would upend the long-standing U.S. policy -- and international consensus -- that the city's status is to be negotiated between Israel and the Palestinians.

The Palestinians seek east Jerusalem -- captured by Israel in 1967 -- as the capital of their future state.

Earlier Tuesday, Palestinian President Mahmoud Abbas warned Trump of "the gravity of the consequences" that the embassy move would have "for the peace process and security and stability in the region and world," according to the Palestinian news agency Wafa.

A 1995 law stipulates that the United States relocate its diplomatic presence to Jerusalem unless the president signs a waiver every six months to keep it in Tel Aviv for national security reasons.

Trump, who took office in January, signed the waiver six months ago because his administration has promoted Middle East peace talks. The deadline of that waiver was Monday.

One administration official on Tuesday defended Trump's planned action, saying the "policy of ambiguity" has not worked in 22 years and the president does not believe the issue will be resolved by ignoring "the simple truth" that Jerusalem is the capital of Israel.

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.

Another official said, "Delaying the recognition of Jerusalem as the capital of Israel has done nothing to achieve peace for more than two decades."

In separate telephone talks Tuesday, Trump informed the leaders of Israel, the Palestinian Authority, Jordan and Egypt of his intention to move the U.S. embassy from Tel Aviv to Jerusalem, the Israeli paper The Jerusalem Post reported in its online edition.

Abbas' diplomatic adviser Majdi Khaldi said the Palestinian leadership would "stop contacts" with the United States if Trump recognizes Jerusalem as Israel's capital, the Associated Press reported in a dispatch from Jerusalem.

Khaldi was quoted as saying the United States would lose credibility as a Middle East mediator if Trump goes ahead with the move.