For more than 40 years, the United States has been at the forefront of international efforts to control the spread of nuclear weapons. From Pakistan to Pyongyang, it has played a crucial role in curbing their proliferation.
Now these decades of hard work have been undermined gravely by Republican senators intent on pursuing a narrow political agenda.
Fortunately, their rejection of US ratification of the Comprehensive Test Ban Treaty may not lead to an immediate resumption of nuclear tests. The Clinton administration has promised to continue its present test moratorium and other countries reacted calmly yesterday. But, in the long run, the situation is far more dangerous.
India and Pakistan, which had been moving towards signing the treaty, will now be less willing to do so. China and Russia also are likely to delay ratification.
As shown by last year's series of tit-for-tat explosions by New Delhi and Islamabad, when one country resumes testing others feel compelled to follow suit. After this week's coup in Pakistan, which is likely to curtail its foreign aid allotments, the fear is that an isolated and impoverished military regime will now feel more inclined to play its nuclear card. That could provoke tests by not only India but also China. Worse still is the danger of wider fallout as a result of the Senate vote.
While not directly related to the proliferation issue, some impact is inevitable. North Korea will use it as ammunition in the brinkmanship over its nuclear programme.
Many other non-nuclear nations were reluctant to accept the treaty's permanent extension. They only agreed to forgo any chance of acquiring such weapons in return for the Clinton administration's pledge to seek a lasting ban on tests by those who already possess them.
Now this tacit deal has come unstuck, with potentially disastrous consequences. None of this need have happened.
If senators had really been motivated by concern that a test ban would jeopardise US security by making it hard to maintain a reliable nuclear arsenal, they could have accepted the White House offer to defer a decision on the issue.
Instead, they insisted on pushing for a vote mainly to inflict a defeat on President Bill Clinton. Such short-sighted behaviour has harmed the interests of not only the US but also the whole world.