Pakistan's status as a key US anti-terror ally faced new scrutiny after weekend reports here that Islamabad had been involved in selling nuclear secrets to the Islamic Republic, following reports last year of previous such links to North Korea.

State Department spokesman Richard Boucher referred reporters to remarks made by Secretary of State Colin Powell in October 2002, after he addressed the matter with Pakistani President Pervez Musharraf.

"He assured us that Pakistan was not participating in any kind of activity of that nature, and I checked this morning and I would say that we continue to accept that assurance," said Boucher.

Powell, at that time, and aides ever since, have pointedly not ruled out previous nuclear transgressions by Pakistan.

Pakistani Foreign Ministry spokesman Masood Khan said Musharraf's government had never authorized or initiated any transfers of sensitive nuclear technology," adding however that several nuclear scientists were under investigation.

"Pakistan takes its responsibility as a nuclear weapons state very seriously. Since a strict command and control system was established nothing of the sort has happened," he said.

Khan denied reports in the Washington Post that US investigators were involved in questioning Pakistani scientists.

"These are purely in-house investigations. No foreigners or foreign agencies are associated with the debriefing sessions in sensitive organisations."

The New York Times reported Monday that information Iran turned over to the International Atomic Energy Agency two months ago has strengthened suspicions that Pakistan sold key nuclear secrets to Iran.

Pakistan's suspected role in providing centrifuge designs to Iran was first reported Sunday in the Post, which said the blueprints provided a "tremendous boost" to Iran's pursuit of nuclear weapons.

WAR.WIRE