US President Donald Trump has threatened to cut off American funding to countries which support a resolution criticising his decision to recognise Jerusalem as Israel's capital.

"We'll save a lot. We don't care," he said, alluding to US aid.

The president strongly supported US Ambassador Nikki Haley who said that the United States "will be taking names" of countries that vote in favour of a General Assembly resolution declaring that Jerusalem's status can be changed only by direct Israeli-Palestinian negotiations.

"For all these nations, they take our money and then vote against us. They take hundreds of millions of dollars, even billions of dollars and then they vote against us," Trump told reporters at a Cabinet meeting in Washington with Haley sitting nearby. "We're watching those votes. Let them vote against us."

What impact the threats from Trump and Haley will have remains to be seen.

Israel has also been conducting a global lobbying campaign against the resolution, government officials said. 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.

The Palestinians 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.

Unlike the Security Council, assembly resolutions are not legally binding but they do reflect world opinion.

In Wednesday's letter, reportedly sent to over 180 countries, Haley said 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 president will be watching this vote carefully and has requested I report back on those countries who voted against us," she wrote in the letter obtained by AP. "We will take note of each and every vote on this issue."