The 'rolling up' of the nuclear proliferation network headed by Pakistani scientist A Q Khan was one of the most 'significant counter-proliferation successes in years' but others could now adapt to evade such investigations in future, the US Central Intelligence Agency has warned.

CIA director George Tenet told the Senate Select Committee on Intelligence in Washington on Tuesday, "Every public success we enjoy can be used by people like Khan to adjust, adapt and evade. Proliferators hiding among legitimate businesses and countries hiding their programmes for manufacturing weapons of mass destruction inside legitimate dual-use industries, combine to make private entrepreneurs dealing in lethal goods one of our most difficult intelligence challenges."

Khan had recently confessed to passing on nuclear technology to Iran, Libya and North Korea. Pakistan President Gen Pervez Musharraf has, however, pardoned him.

Tenet said Khan and his network had been unique in being able to offer 'one-stop shopping' for enrichment technology and information on weapons design.

"With such assistance, a potentially wide range of countries could leapfrog the slow, incremental stages of nuclear weapons development programmes," he said.