Palestinians call the planned move a war crime under international law governing the occupied West Bank. Arab League and Jordon say the move would "push the region towards violence."
Israeli Prime Minister Benjamin Netanyahu announced his intention on Tuesday to annex the Jordan Valley in the occupied West Bank if he wins next week's general election on September 17.
Palestinian chief peace negotiator Saeb Erekat called the planned move a war crime under international law governing occupied territory.
"There is one place where we can apply Israeli sovereignty immediately after the elections," Netanyahu said in a speech broadcast live on Israeli TV channels.
"If I receive from you, citizens of Israel, a clear mandate to do so...Today, I announce my intention, after the establishment of a new government, to apply Israeli sovereignty to the Jordan Valley and the northern Dead Sea," Netanyahu said in a speech broadcast live on Israeli TV channels.
Netanyahu, who is fighting for his political life in a closely-contested election reaffirmed a pledge to annex parts of occupied West Bank but said such a move would not be made before publication of a long-awaited US "peace plan" and consultations with President Donald Trump.
Trump's long-awaited peace plan is expected to be unveiled sometime after the vote.
There was no immediate comment from Washington.
Netanyahu made no mention of what he would do with the territory's more than two million Palestinian residents.
Palestinian Prime Minister Mohammad Shtayyeh said that the Israeli leader is "a prime destroyer of the peace process".
A senior Palestinian official said Netanyahu's pledge to annex the Jordan Valley if re-elected destroyed all chances of Israeli-Palestinian peace.
"He is not only destroying the two-state solution, he is destroying all chances of peace," senior official Hanan Ashrawi told AFP news agency. "This is a total game-changer."
World leaders are denouncing Netanyahu's decision.
Turkey's foreign minister slammed Israel's prime minister over his illegal, unlawful and aggressive messages in election pledges, saying they are part of a "racist apartheid state."
Turkey will defend the rights and interests of "our Palestinian brothers and sisters till the end," Cavusoglu added.
Stephane Dujarric, a United Nations spokesman, said Tuesday that the organization maintains that any Israeli move to impose its administration over the Palestinian territory "would be devastating to the potential of reviving negotiations, regional peace and the very essence of a two-state solution."
The Arab League also condemned Netanyahu's remarks as "a serious development and an Israeli aggression" that, if carried out, amount to "an Israeli declaration for the end of the peace process."
Jordan's foreign minister, Ayman Safadi, said in a statement that annexation of Israel's West Bank settlements would fan the flames of conflict around the region
The election promise of Netanyahu, who is giving all kind of illegal, unlawful and aggressive messages before the election, is a racist apartheid state. Will defend rights and interests of our Palestinian brothers&sisters till the end.— Mevlüt Çavuşoğlu (@MevlutCavusoglu) September 10, 2019
The Jordan Valley, which Palestinians seek for the eastern perimeter of a state in the West Bank and Gaza, stretches from the Dead Sea in the south to the Israeli city of Beit Shean in the north. Israel captured and occupied the West Bank in a 1967 war.
The 2,400 sq km valley accounts for nearly 30 percent of the territory in the West Bank. Israel has long said it intends to maintain military control there under any peace agreement with the Palestinians.