The UN General Assembly will vote Thursday on a US-drafted resolution that would condemn the Palestinian Hamas movement, a measure championed by US Ambassador Nikki Haley.
The United States won crucial backing from the European Union for the draft resolution that condemns the firing by Hamas of rockets into Israel and demands an end to the violence.
If adopted, it would mark the first time that the assembly has taken aim at Hamas, the Islamist militant group that has ruled the Gaza Strip since 2007.
All 28 EU countries agreed to support the measure after the United States included a mention of relevant UN resolutions in the text that does not however refer to the two-state solution.
In a statement, the US mission to the United Nations said it had hoped to put the draft resolution to a vote on Monday but that the Palestinians had pushed for a delay until Thursday.
"The issue before the United Nations on Thursday is not whether it supports one form or another of a Middle East peace plan," the US mission said.
"Each country will be asked to vote for or against the activities of Hamas, along with other militant groups like Palestinian Islamic Jihad."
"If the UN cannot bring itself to adopt this resolution, then it has no business being involved in peace discussions," it added.
The European Union, like the United States, considers Hamas a terror group, but the 28-nation bloc is divided over how to support peace efforts.
Haley, who will step down as UN ambassador in January, has steadfastly supported Israel in its confrontation with Hamas and chastised the United Nations for criticizing both sides.
The vote on Thursday will follow the adoption in the assembly of about a dozen resolutions on the Israeli-Palestinian conflict that condemn Israeli settlements and call for progress toward the two-state solution.
Resolutions adopted by the General Assembly are non-binding, but they carry political weight and are seen as a barometer of world opinion.
The United States put forward the resolution as it prepares to unveil new peace proposals that the Palestinians have already rejected.
The Palestinians have severed ties with the administration of President Donald Trump after the decision nearly a year ago to move the US embassy to Jerusalem and declare the city Israel's capital.
The US administration has also cut more than $500 million in Palestinian aid.
The Palestinians see the city as the capital of their future state. International consensus has been that Jerusalem's status must be negotiated between the two sides.