US President Donald Trump has threatened to cut financial aid to countries that vote against his move to recognise Jerusalem as Israel's capital.
With his 6 December decision, Mr Trump reversed decades of US policy and upset an international consensus enshrined in UN resolutions that treats Jerusalem's status as unresolved.
It stirred outrage among Palestinians and in the Arab world, and raised concern among Washington's Western allies. Israel captured East Jerusalem in a 1967 war and Palestinians want it as the capital of a future state they seek.
Palestinian UN envoy Riyad Mansour has said the General Assembly would vote on a draft resolution calling for the US declaration to be withdrawn. Such a vote is non-binding, but carries political weight.
The rare emergency session of the 193-member UN General Assembly was called at the request of Arab and Muslim states.
"They take hundreds of millions of dollars and even billions of dollars, and then they vote against us," said Mr Trump at the White House.
"Well, we're watching those votes. Let them vote against us. We'll save a lot. We don't care."
On Monday, the US vetoed a UN Security Council draft resolution that called on it to withdraw its declaration.
The remaining 14 Security Council members, including close US allies such as Japan and four European Union countries, voted in favour of the Egyptian-drafted resolution which did not specifically mention the United States or Trump but which expressed "deep regret at recent decisions concerning the status of Jerusalem."
"On Thursday there'll be a vote criticizing our choice," US Ambassador to the UN Nikki Haley said on Twitter. "The US will be taking names."
Foreign minister Mevlut Cavusoglu of Turkey, which has led Muslim opposition to the move, said that was a threat and called on Washington to change course.
"We expect strong support at the UN vote, but we see that the United States, which was left alone, is now resorting to threats. No honourable, dignified country would bow down to this pressure," Mr Cavusoglu told a news conference held alongside his Palestinian counterpart Riyad al-Maliki.
"We want America to turn back from this wrong and unacceptable decision," Mr Cavusoglu said earlier in the Azerbaijani capital Baku, where he met with Iranian and Azeri ministers.
"God willing, we will push through the General Assembly a resolution in favour of Palestine and Jerusalem," he said.
Turkish President Tayyip Erdogan has lambasted Trump's move, and hosted a summit of Muslim leaders last week calling for East Jerusalem to be recognised as the capital of Palestine. Israel calls Jerusalem its indivisible and eternal capital.
"From now on we will be more active in defending the rights of Palestinians. We will work harder for the international recognition of an independent Palestinian state," Cavusoglu told reporters in Baku.