The sanctions were notified in the Federal Register on Monday by the State Departments Bureau of Political and Military Affairs. The sanctions usually run for two years, official sources told The Indian Express.

The sanctions against Pakistan, which kicked in on April 17 and were spelled out on April 24, are of Category One type. This means only the institution involved in missile proliferation (in this case Khan Research Laboratories) and its sub-units and successors are affected, sparing the rest of the relationship.) In the case of North Korea, although, the notification names the Changgwang Sinyong Corporation (aka North Korea Mining Development Trading Corporation) (North Korea) and its sub-units, successors, and affiliated companies, the whole country is sanctioned under special country-specific amendment instituted by SenatorJesse Helms.

Under the sanctions, new individual licenses for export of items controlled by the Export Administration Act of 1979 and the Arms Export Control Act will be denied for two years. The US will also not enter into contracts involving the entities or import anything from them for two years.

Administration sources said Pakistan had already been notified about the sanctions. Islamabad has been blase about ban, saying the embargo was meaningless because Khan Research Laboratories does not export or import anything to or from the United States. North Korea too does not have any institutional ties with the US.

But analysts say the rap on the knuckles is an expression of US concern over covert missile proliferation and an indication that existing laws kick in automatically when violations occur. Washington had similarly sanctioned entities in China and Pakistan five years ago over the supply to Islamabad of nuclear-capable M-11 missiles. India's ISRO has also been sanctioned under the same US law.Other experts say the latest sanction is just another wrinkle in US-Pak ties. In fact, the buzz in the field is that Washington is considering some action to reimburse Pakistan for the sequestered F-16s before President Clinton embarks on his South Asia trip in November this year.

The deal could involve a debt write-off or upgrading Pakistan's existing fleet of F-16s. Ideas are already being tossed between administration officials and influential law makers who are sympathetic to the Pakistan's misery on the f-16 score.

The planes have now been lying idle at a desert air base for close to five years, because the Pressler Amendment throttled the sale on account of Pakistan crossing the nuclear threshold.