The US is seeking to renew the immunity from prosecution enjoyed by American peacekeepers, with a resolution before the UN Security Council.
But human rights campaigners said the Iraq prison abuse scandal proves that the US needs to be held to account.
"Given the recent revelations... the US has picked one hell of a moment to ask for special treatment," said Richard Dicker of Human Rights Watch.
A number of Security Council members are expected to abstain from the vote.
Annual renewal
The US Deputy Ambassador to the UN, James Cunningham, insisted that those behind the abuse scandal would be "held fully accountable" by the US itself.
Washington negotiated special dispensation when the International Criminal Court came into being two years ago, arguing that as the world's only superpower, it might be subject to spurious or malicious prosecutions.
The US secured the UN's agreement by threatening to veto all its peacekeeping operations.
The exemption - which gives US soldiers immunity from international prosecution when serving on UN-backed missions - was passed in 2002 on an annual-renewal basis.
Last year, the vote passed 12-0, with France, Germany and Syria abstaining.
'Not automatic'
But after the revelations of torture in US-run prisons in Iraq, it is thought more countries may refuse to back the motion this time.
"There's growing opposition to this resolution and it's going to be reflected in an increase in the number of abstentions over last year", said Mr Dicker.
"Last year, it was more of an abstract question, but this year with the prisoner abuse scandal in Iraq it takes on a more sinister meaning."
The matter was due for discussion at the Security Council in New York on Friday.
But the vote has been delayed until Monday at the request of the Chinese UN ambassador, who is awaiting instructions from Beijing on how to vote.
The US needs nine votes for the resolution to be adopted - and no veto from the other four permanent members, Britain, France, China and Russia.
The current year's exemption ends in June. But last year, UN Secretary General Kofi Annan warned the renewal should not become an "annual routine."
Washington has also signed bilateral agreements with 89 countries to ensure they do not prosecute US personnel - although only 63 of those countries have been named publicly.
Only one country of the 63 is on the UN Security Council - the Philippines.
http://news.bbc.co.uk/1/hi/world/americas/3736683.stm
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