The European Council has warned companies they could face "legal, economic and reputational consequences" if they involve themselves with East 1 (East 1) settlement construction in the Israeli-occupied West Bank.
The major intervention on Friday, from the body that determines the European Union's political direction, came just days before the 19 October deadline for bids in one of the E1 settlement construction tenders.
The Israeli government's E1 settlement plan involves building thousands of new housing units between Jerusalem and the existing West Bank settlement of Maale Adumim, 7km east of the city.
It aims to connect settlements in the West Bank with occupied East Jerusalem and would effectively cut the West Bank in half, making a Palestinian state unviable.
The European Council urged "Israel to immediately reverse the expansion of settlements, which are illegal under international law, including by withdrawing its tender for construction in the E1 area".