If US officials hope to make progress in their nuclear negotiations with North Korea, one task cannot be ignored: ending Pyongyang's highly enriched uranium programme. It would be a serious mistake, in the wake of the agreement reached in the six-party talks last month, to downplay the significance of the HEU programme.

Some US policymakers suggested that the US intelligence community is uncertain about the HEU programme, perhaps as a way of lowering the bar for North Korean compliance by allowing them to admit to only an experimental HEU programme. Such tactics, however, reduce Washington's negotiating leverage and we can expect North Korean negotiators to exploit it.

Discussions with former senior US government officials indicate that the intelligence community was unanimous in its 2002 assessment that North Korea had an active programme to acquire materials for enriching sufficient uranium to develop weapons. Where disagreements existed, they were over the extent of progress North Korea had made, or was likely to make, towards achieving a covert capability to produce uranium.

But pursuit of an HEU programme, regardless of progress, violates North Korea's commitments to the 1994 "agreed framework" - in which North Korea first pledged to freeze its nuclear programme in return for energy assistance - the Nuclear Non-Proliferation Treaty, International Atomic Energy Agency safeguards and the 1992 North-South Korea de-nuclearisation accord.

Given intelligence estimates that, left unchecked, Pyongyang would be able to manufacture uranium weapons within several years, US policymakers decided in 2002 to challenge North Korea. Officials present during the meeting with North Korean officials that year confirm that they acknowledged such a programme.

Pakistan's President Pervez Musharraf subsequently admitted that renegade nuclear scientist Abdul Qadeer Khan had sold at least 20 centrifuges to North Korea for the purpose of enriching uranium for a weapon.

Joseph DeTrani, America's chief intelligence officer for North Korea, told a congressional panel last month that the US had high confidence in 2002 that North Korea was pursuing an HEU programme and had never walked away from that judgment. There is now less certainty, however, over how much progress North Korea has made since the 2002 confrontation. North Korea's lack of success in completing the programme may be due to technical difficulties or because international non-proliferation pressure and financial restrictions impeded Pyongyang.

To enable a comprehensive public debate over future six-party talks agreements, the US intelligence community should prepare an unclassified national intelligence estimate that updates its assessments of North Korea's nuclear weapons and missile programmes. A corresponding classified version would allow congressional committees to serve their proxy role for US citizens on intelligence matters.

During forthcoming working-group meetings for the six-party talks, US officials should insist that North Korea fully disclose all of its plutonium and uranium-related facilities, including geographic co-ordinates and function, as well as list all production equipment, fissile material and nuclear weapons. Pyongyang should provide this within 30 days of the initial working group meeting and be warned that any omissions will hamper its eligibility for receiving benefits.

Verification will be the key to preventing North Korea from cheating again on its international commitments. We need a rigorous and invasive verification regime, similar to that of the Strategic Arms Reduction, Intermediate-Range Nuclear Forces and Conventional Armed Forces in Europe treaties. Washington must insist on the right to conduct short-notice challenge inspections of non-declared facilities for the duration of the agreement.

The de-nuclearisation working group should also outline procedures for unrestricted IAEA inspections throughout North Korea. And we should link the provision of significant benefits to North Korea implementing verification procedures. The six-party talks participants should not replicate provisions in the agreed framework that allowed North Korea to defer IAEA inspections of suspect nuclear sites for years.

Only by achieving total transparency of Pyongyang's nuclear programme through extensive verification measures can the six-party talks achieve the de-nuclearisation of North Korea.

Bruce Klingner is senior research fellow for northeast Asia.