Washington: The mystery over arms shipments to Pakistan continues. Two things are clear: that an embargo was imposed by the US in March; and that arms are still reaching Pakistan. American attempts to explain the situation are, however, gloriously confused. US officials in Pakistan have claimed Washington purposely continued the arms flow in secret in order to retain some influence of the treatment accorded Bengalis. In Washington it was maintained they were still being sent because President Richard Nixon didn't want China to become Pakistan's sole arms supplier.

Last weekend the refusal of American longshoremen to load the Padma brought the affair into sharp focus without however clarifying anything. The US state department, having announced in April that no arms had "been provided to the Pakistan government or its agents since March 25 and nothing is now scheduled for such delivery", stated the Pakistani freighter had contracted to carry exactly US$1,231,158 worth of arms, some of which had already been loaded in New York, the rest to join the ship at Baltimore. It included three Poston aircraft engines and an aircraft repair test stand.

On Sunday the Padma set sail, with the Baltimore dockers surprisingly expressing themselves convinced by an assurance from the owners, backed by International Longshoremen's Association President Thomas Gleason, that there were no arms on board. There was no comment from Washington.

If the state department had its facts wrong, it was politically a remarkable error. And it had been unaccustomedly precise. Was it trying to anticipate a public row, or replying to the New York Times - which had made the original discovery about the Padma when it was being loaded in New York?

Or was it retaliating on the president for putting it in an impossible position? It appears the embargo had been proposed, vetoed by Nixon - and then announced anyway. Less than a month later another Pakistani vessel, the Sunderbans, was steaming home with a load of armoured personnel carriers. Several more shiploads are scheduled. State department officials were torn between denying all knowledge of the shipments, admitting to "some kind of slippage" and claiming all that had originally been meant was that no more licences would be issued - which would leave weapons in the pipeline valued by one US senator at $35 million.

The sale of arms to Pakistan has had a murky history since 1965, when the first embargo was placed on both India and Pakistan. Sales resumed two years later of weapons termed "nonlethal" a category which soon appeared to include any weapon the government finds embarrassing to describe in greater detail, and covered shipments put at up to $20 million a year in value.

Meantime, Pakistan has served a useful purpose as a secret take-off pad for Kissinger. Islamabad must be hoping Nixon will appreciate its cooperation more than the views of informed opinion at home.