The Federal Government says it will seek clemency for an Australian man sentenced to death by a court in Singapore.

Van Tuong Nguyen, 23, has been convicted for possessing heroin.

The Foreign Affairs Department says the Howard Government will maintain a long- standing opposition to the death penalty.

It will ask Singapore's President to grant clemency.

Nguyen was arrested in December 2002 at Changi International Airport as he tried to board a flight to Melbourne.

Security officials found 400 grams of heroin taped to his back and inside a backpack.

The judge took less than a minute to deliver the verdict against Nguyen, declaring he would be taken to a place of custody to be hanged by the neck until he was dead.

Under Singapore's strict anti-drug laws, anyone found with more than 15 grams of heroin faces a mandatory death penalty.

Nguyen said, "tell my family I love them" as he was led away.

Nguyen's lawyers have two weeks to file an appeal to the High Court but they say, based on past experience, it is unlikely to be successful.

By South-East Asia correspondent Peter Lloyd