TEHRAN, June 3, 2008 (AFP) - Supreme leader Ayatollah Ali Khamenei on Tuesday warned Iranian youths that the nation's Western enemies were seeking to weaken them with plots aimed at spreading sexual depravity and drug addiction.

'Today, combating organised plots pushing the Iranian youth towards carnal desires, drugs or sexuality is a prime duty of the Iranian people and especially the young,' Khamenei said in a speech broadcast on state television.

He warned that Iran's youth needed to be hard-working and innovative in order for the country achieve progress and its enemies were plotting to distract them through sex and drugs.

'They try to mislead the Iranian youth by spreading depravity, prostitution, and drugs through gangs,' he said in the speech marking the anniversary of the 1989 death of revolutionary leader Ayatollah Ruhollah Khomeini.

'Young people who pay attention to sexual and carnal desires or are held hostage to drugs no longer want to work and have no innovation, determination or will,' he added.

Iranian officials openly admit there is a serious drug abuse problem in the country, which is situated along one of the main trafficking routes for cannabis, heroin, opium and morphine produced in Afghanistan.

Out of 2,500 tonnes of narcotics that enter Iran from neighbouring Afghanistan annually, some 700 tonnes are consumed in the country, officials say.

Designer drugs have also found their way into the Iranian market in recent years.

Khamenei described the fight against drugs in Iran as a 'great jihad and a fundamental task in the progress of the Iranian nation.'

Sex outside of marriage is strictly prohibited in Iran but in practice the law is not always followed behind closed doors. Temporary marriage to relieve sexual urges is allowed however, in a practice unique to Shiite Islam.