The EU has indicated that it will try to stop Israel's proposed annexation of parts of the occupied West Bank.
Foreign policy chief Josep Borrell said the bloc would use its diplomatic clout to prevent unilateral action.
Israel's incoming unity government has agreed that the process of annexing West Bank settlements and the Jordan Valley could begin as early as July.
The Palestinians, who seek a state which includes all of the West Bank, bitterly oppose the idea.
Speaking after a virtual meeting of EU foreign ministers, Mr Borrell said: "We must work to discourage any possible initiative toward annexation."
He said the EU looked forward to working with Israel's new government, but added: "Unilateral action from either side should be avoided and for sure international law should be upheld."
Some EU states are said to be calling for a tougher line on the issue, including possible sanctions, but others have urged caution.
"What everybody agreed is we have to increase our efforts and our reach-out to all relevant actors in the Middle East," Mr Borrell said.
The application of Israeli sovereignty over parts of the West Bank is in line with US President Donald Trump's "vision for peace" between Israel and the Palestinians, which was unveiled in January.
Mr Trump's plan also envisages a Palestinian state in about 70% of the West Bank, all of Gaza, and with its capital on the fringes of East Jerusalem.
The Palestinians - who claim the West Bank, Gaza and East Jerusalem - have rejected the US plan, dismissing it as biased towards Israel and a denial of their rights.
Israel has occupied the territories since the 1967 Middle East war. More than 600,000 Jews live in about 140 settlements in the West Bank and East Jerusalem. Most of the international community considers the settlements illegal under international law, though Israel disputes this.
This is what a future State of Palestine can look like, with a capital in parts of East Jerusalem. pic.twitter.com/39vw3pPrAL— Donald J. Trump (@realDonaldTrump) January 28, 2020
Israeli Prime Minister Benjamin Netanyahu pledged to annex all Jewish settlements during his electoral campaign in January, and secured the agreement of his political rival, Benny Gantz, to push ahead with the issue as part of a power-sharing deal between the two men.
The terms of the agreement say the legislative process can begin from 1 July and that Mr Netanyahu and Mr Gantz will act "in full agreement with the US... and in dialogue with the international community".
In a visit this month, US Secretary of State Mike Pompeo said it was Israel's decision on how to move forward.
In an interview with the Israel Hayom newspaper, he noted the issue was complex and required coordination with Washington. Some observers saw this comment as a veiled warning to Israel to proceed with caution.
Arab countries, including Jordan and Egypt, have also cautioned against Israeli annexation moves.