'This is obviously a very sensitive topic,' White House spokesman Robert Gibbs told reporters earlier in Washington. 'We will hope to provide some more detail at a later point. Our focus right now is ensuring the safety of the two journalists that are in North Korea right now.'

Clinton was greeted by high-ranking North Korean officials upon his arrival, including Kim Kye Gwan, North Korea's top nuclear negotiator, state-run Central Television said. Some analysts speculated that Clinton's trip could be a catalyst for thawing relations and resuming negotiations on Pyongyang's contentious nuclear programme.

North Korean media reported that Clinton and Kim Jong Il engaged in 'serious conversation.' The White House flatly denied a North Korean media report that Clinton had delivered a personal message from President Barack Obama to Kim.

There was hope that Clinton's visit could pave the way for the US and North Korea to begin making progress on stalled negotiations over Pyongyang's nuclear activities.

The talks have been at an impasse since last year, and North Korea announced in January it would no longer participate in the six-nation talks aimed at resolving the nuclear dispute. The other countries are China, Japan, Russia and South Korea.

North Korea recently signalled its interest in one-on-one discussions with the US. Washington said it would be willing for direct communication in the context of the six-nation format, but not until Pyongyang takes steps to live up to its obligations in a 2005 disarmament agreement.