Antonio Guterres, the secretary-general of the United Nations, has urged Israel to drop plans to annex parts of the West Bank, which could begin as early as next month.

At a meeting of the UN Security Council on Wednesday, he warned that annexation would “constitute a most serious violation of international law, grievously harm the prospect of a two-state solution and undercut the possibilities of a renewal of negotiations”.

He called on the Israeli government to “abandon” the scheme.

The peace proposals published by American President Donald Trump earlier this year envisaged Israel extending sovereignty over a sizeable portion of the West Bank.

Israel’s UN Ambassador Danon told the council, “Should Israel decide to extend its sovereignty, it would be doing so with respect to areas over which it has always maintained a legitimate historical and legal claim.”

But Ahmed Aboul Gheit, secretary general of the Arab League, warned that any Israeli move to annex territory would “destroy any prospects for peace in the future”.

Mr Gutteres called on the so-called Quartet – the USA, Russia, the UN and the European Union – to bring the Israelis and Palestinians together.

White House officials discussed on Wednesday whether the American administration should approve any unilateral move by Israel.

American Secretary of State Mike Pompeo said, “The decisions about Israel extending sovereignty towards these places are decisions for the Israelis to make. We are talking to all of the countries in the region about how it is we can manage this process.”

He voiced regret that the Palestinians – who have rejected the Trump proposals – had refused to participate in talks.

Although Mr Netanyahu has repeatedly said he would begin implementing the annexation plan from July 1, Israeli media have suggested that it might involve a more scaled-back version that extended to some settlements.

The country’s Foreign Minister Gabi Ashkenazi was reported to have said earlier this week that he assumed it would not include the Jordan Valley.

Earlier this week 1,080 European parliamentarians include 240 from the UK signed a letter in opposition to any annexation move.