UNITED NATIONS  The General Assembly is preparing to approve a resolution that would endorse a United Nations report calling on both Israel and the Palestinians to investigate possible war crimes in the Gaza Strip within three months.

The assembly began discussing the nonbinding resolution, introduced by about 20 Arab League members, including Iraq, on Wednesday, but with about 50 nations scheduled to speak, a vote was not likely until Thursday. Given the widespread support for the Palestinian cause and broad criticism of Israel, passage of the measure seemed assured.

Some members of the European Union were threatening to abstain, however, holding out for changes. One issue was wording that would require Secretary General Ban Ki-moon to work with the Security Council on additional action; another was the resolution’s full endorsement of a decision last month by the United Nations Human Rights Council to adopt the report completely, diplomats said.

The 575-page report, which was released in September, found evidence of war crimes committed by both the Israeli Army and Hamas fighters during the Gaza war last winter. The report was researched and written by a fact-finding mission created by the Human Rights Council and led by Richard Goldstone, a South African judge and a former war crimes prosecutor for Rwanda and the former Yugoslavia.