Donald Trump has threatened to withdraw US aid to countries who vote for a UN resolution calling for the president to go back on his decision to recognise Jerusalem as Israel's capital.
The US ambassador to the UN Nikki Haley had hinted in a tweet and a letter to most of the UN's members states on Tuesday that the US would retaliate against countries who voted in favour of the resolution.
The president went further at the start of a cabinet meeting on Wednesday, saying some countries take "billions of dollars" from the US, adding: "We'll save a lot."
Nihad Awad, national executive director of the Council on American-Islamic Relations, tweeted after Trump's comments: "Our government should not use its leadership at the UN to bully/blackmail other nations that stand for religious liberty and justice in Jerusalem. Justice is a core value of Christianity, Judaism and Islam."
The Palestinians and their Arab and Islamic supporters sought the General Assembly vote after the United States on Monday vetoed a resolution supported by the 14 other UN Security Council members that would have required Trump to rescind his declaration on Jerusalem as Israel's capital and not move the US Embassy there.
Before Haley's letter and tweet, Palestinian UN Ambassador Riyad Mansour said he expected "massive support" for the resolution in the General Assembly.
Palestinian Foreign Minister Riyad al-Maliki and Turkish Foreign Minister Mevlut Cavusoglu accused the US of intimidation.
Some diplomats predict the resolution will be supported by at least 150 countries, and possibly 180 nations.
Israel has also been conducting a global lobbying campaign against the resolution, government officials said Wednesday. The vote will show whether Prime Minister Benjamin Netanyahu has succeeded in his efforts to drum up new pockets of support in the developing world.
Haley said in her letter, reportedly sent to over 180 countries, that the Trump administration is "simply asking that you acknowledge the historical friendship, partnership, and support we have extended and respect our decision about our own embassy."
The vote is due to take place later today.