Several nations on Tuesday immediately vowed to disregard the non-binding statement, which was approved in a 84-34 vote with 37 abstentions after four years of often bitter debate about the meaning of human life.
All UN member nations agreed that cloning should be banned for the purposes of producing adult copies of human beings, but there has been sharp disagreement over the validity of therapeutic cloning.
Many scientists say therapeutic cloning - in which embryos are cloned to produce stem cells for medical research before the embryos are later destroyed - could help find a cure for diseases such as Alzheimer's and cancer.
The US administration of President George Bush, however, argued that such research ultimately entails the destruction of human life and should also be outlawed.
Washington then helped lead opposition to a declaration that would have come out against reproductive cloning while leaving the question of cloning for medical research up to individual nations.
"We cannot allow such an ambiguous declaration which may sow confusion about the acceptability of this important field of research"
Emyr Jones Parry,
Britain's ambassador to the UN
With many Islamic countries abstaining for lack of a consensus on the issue, the non-binding declaration was approved - just as it did when brought up before a UN committee last month.
China, Belgium and key US ally Britain immediately indicated that the assembly decision would not change their position in favour of cloning for medical research.
Without naming the United States, Britain's UN ambassador Emyr Jones Parry lashed out at the "intransigence of those who are not prepared to recognise that other sovereign states" might support cloning for medical research.
"We cannot allow such an ambiguous declaration which may sow confusion about the acceptability of this important field of research," Jones Parry said after the vote.