Israel's Prime Minister Benjamin Netanyahu pledged to extend the country's sovereignty over the Jordan Valley and the northern Dead Sea.
Arab and Muslim countries on Wednesday led a wave of outcry after Israeli Prime Minister Benjamin Netanyahu vowed to annex a key part of the occupied West Bank if re-elected.
Netanyahu's controversial pledge involves extending Israel's sovereignty over the Jordan Valley and the northern Dead Sea which account for one-third of the West Bank if he wins next week's elections. It would not include however annexing any Palestinian cities such as Jericho.
The pre-election promise late on Tuesday drew immediate condemnation from Arab powerhouses with many warning of disastrous consequences for the stagnant Israeli-Palestinian peace process.
"The announcement constitutes a dangerous development and a new Israeli aggression," Arab foreign ministers said.
UN Secretary General Antonio Guterres also expressed concern on Wednesday about Netanyahu's plan, saying it would be illegal and gut prospects for regional peace.
"Such steps, if implemented, would constitute a serious violation of international law," he said in a statement. "They would be devastating to the potential of reviving negotiations and regional peace, while severely undermining the viability of the two-State solution."
'Illegal and irresponsible'
They also warned in a statement of "the ramifications of these dangerous, illegal and irresponsible" moves saying it would "undermine the chances of progress in the peace process".
Jordanian and Palestinian officials said any such measure risks "killing off" and "destroying" the entire peace process.
Jordan's house speaker Atef al-Tarawneh went as far as to warn on Wednesday that any such move could even put Israel's peace treaty with the country – only one of two with Arab states – at stake.
Damascus "strongly condemned" Netanyahu's vow, with a Syrian foreign ministry source telling the state news agency SANA that it was an "expansionist" plan in "flagrant violation" of international treaties.
The Syrian regime's main backer Russia warned that the plan could lead to a "sharp escalation of tensions in the region (and) undermine hopes for the establishment of long-awaited peace between Israel and its Arab neighbours".
Israel occupied the West Bank in the 1967 Six-Day War in a move never recognised by the international community.
It also seized – and later annexed – part of the Golan Heights from Syria, and the two countries remain technically at war.
Saudi Arabia flagged the announcement as a "dangerous escalation", and convened an "emergency meeting" of the foreign ministers of the 57 member states of the Organisation of Islamic Cooperation (OIC) in Jeddah on Sunday to discuss the issue.
United Arab Emirates' foreign minister Abdullah bin Zayed al Nahyan denounced Netanyahu's proposal as "electoral exploitation in the most heinous form".
The Gulf Cooperation Council's chief Abdellatif al-Zayani characterised the Israeli prime minister's rhetoric as a "dangerous and aggressive provocation".
But Lebanon's Hezbollah movement, which earlier this month exchanged cross-border fire with the Israel army, blamed the Gulf Arab states for emboldening Netanyahu to take stronger steps against the Palestinians.
"Measures toward normalisation and Gulf attempts to foster alliances with the enemy have created an opportunity to chip away at more Arab lands," the group said in a statement.
Turkey slammed Netanyahu's pledge as "racist" and vowed to "defend (the) rights and interests of our Palestinian brothers and sisters till the end".
The United Nations said Netanyahu's plan would have no "international legal effect", and the European Union said it undermined any prospects for peace.
"The policy of settlement construction and expansion... is illegal under international law and its continuation, and actions taken in this context, undermine the viability of the two-state solution and the prospects for a lasting peace," an EU statement said.
When announcing his pledge, Netanyahu said he would take the step in coordination with his ally, US President Donald Trump.
Israel has enjoyed a strong US support under the Trump administration which in a highly controversial move overturned decades of US policy to recognise the holy city of Jerusalem as the capital of the Jewish state in 2017.
Earlier this year, Trump declared Israeli sovereignty over the Golan Heights, which Israel seized Syria in the 1967 Six-Day War, along with the West Bank and east Jerusalem.
More than 600,000 Israeli Jewish settlers now live in the West Bank and annexed east Jerusalem, among three million Palestinians.
Arab and Muslim leaders have unanimously decried the US moves backing Netanyahu's policies, insisting instead on achieving a two-state solution with east Jerusalem as its capital.
Trump's son-in-law Jared Kushner has been tasked with hammering out a peace plan to resolve the bitter conflict.
The plan's economic aspects were unveiled at a Bahrain conference in June, floating the prospect of pumping some $50 billion worth of investment into a stagnant Palestinian economy.
It failed however to address key Palestinian demands and it remains unclear when Kushner's full plan will be rolled out.