The New York Times says Pakistani nuclear scientist Abdul Qadeer Khan told interrogators he had seen three nuclear devices during a trip to North Korea five years ago.

Quoting Asian and American officials who had been briefed by the Pakistanis, the paper said Tuesday that during the trip to North Korea, Khan said he was taken to a secret underground nuclear plant and saw what he described as nuclear devices.

The daily said that if what Khan said is true, it would be the first time any foreigner has reported seeing a North Korean nuclear weapon.

But the reports added that U.S. intelligence officials are unsure if Khan had the time, expertise or equipment to verify if the devices were indeed nuclear weapons.

In Washington, White House officials declined to discuss the intelligence reports, saying through a spokesman that the subject was "too sensitive."

Meanwhile, State Department spokesman Richard Boucher said Khan's claims must be taken seriously, stressing that North Korea has previously claimed to possess a nuclear deterrent.