Mr Clinton told reporters yesterday that he would make a formal announcement 'in the next few days' - either just before the 7 July G-7 Tokyo summit or during it. 'I've made a decision and we're working out some of the details,' he said. But given Congressional resistance to a resumption, and the administration's commitment to halting nuclear proliferation, there is scant doubt about his choice.
Three options have been on his desk: a go-ahead for a limited series of nine explosions at the Nevada test site between now and 1996, three of which would be by Britain; an unconditional 12-month extension of the current moratorium which technically expires today; or an extension with a clause permitting the US to restart testing if another nuclear power did so first.
The President, officials said yesterday, has all but chosen the third variant. In essence, this marks a second climb down. At first, at the urging of the Pentagon and Energy Department, which runs the three US nuclear laboratories, he indicated he would stick with previous plans for 15 tests by 1996. That was later scaled down to nine.
Now, following public demands by 36 Senators and 100 Congressmen for an extension of the moratorium, he is about to bow once more with the formula of 'no-first-test'.
This would enable the facilities to be kept ticking over, at least until October 1996, the target date for a permanent test ban agreement by the world's five declared nuclear powers. A year before that comes a more important date: the review conference for the 1970 Nuclear Non-Proliferation Treaty.
The Western powers, anxious to prevent the spread of atomic weapons, are seeking an indefinite extension of the treaty. But supporters of arms control say that if the US resumes testing, not only would Britain, France and probably Russia and China follow suit, but the moral basis for efforts to prevent proliferation to countries like Iran, Iraq, Pakistan and North Korea would be fatally undermined.
No-one will be more disappointed than Britain, which is reliant on the Nevada facility and which has been wanting to test a new warhead version under design at the Aldermaston laboratory for use, defence sources say, both in the Trident submarine and for a new tactical 'gravity bomb' which could be employed in a variety of roles. But, sensing the way the wind is blowing, British officials have been downplaying the importance of resumption.
One leading US anti-testing lobbyist said: 'It puts a permanent nuclear testing ban clearly within reach.' Britain's behaviour is being less generously interpreted. Dan Plesch, of the Anglo-US arms control group Basic, said: 'It bodes ill for the entire British approach to non- proliferation if you're going to be dragged kicking and screaming to stop testing, and then pretend that you supported this all along.'