President Yoweri Museveni is asking the US to advise Uganda's scientists about homosexuality, as he considers whether to sign a law increasing punishments.
Mr Museveni's spokesman said the president would not sign the law until he had received the scientific advice.
Last week he said he had decided to sign the Anti-Homosexuality Bill, which parliament has passed.
The US - one of Uganda's largest aid donors - has warned that enacting the bill would complicate relations.
President Barack Obama described it as an affront, and a danger to, Uganda's gay community.
BBC regional analyst Richard Hamilton says President Museveni is trying to please a conservative local constituency while avoiding alienating Western aid donors.
Homosexual acts are already illegal in Uganda. Under the proposed legislation, those convicted could face life imprisonment.
The law would also make it a crime not to report gay people.
'Abnormal'
In a statement, Mr Museveni said: 'I... encourage the US government to help us by working with our scientists to study whether, indeed, there are people who are born homosexual.
'When that is proved, we can review this legislation.'
Presidential spokesman Tamale Mirundi told Reuters news agency the bill would be on hold for now 'until more conclusive research is done, and that's what the president is saying'.
Mr Museveni origin.