The nuclear testing by India and Pakistan raises the stakes in what has become a dangerous three-cornered regional arms race.

China is a declared nuclear power with a significant arsenal of weapons and various means to deliver them. Both India and Pakistan are thought to be capable of putting together nuclear weapons in a reasonably short space of time.

Neither claims to have deployed nuclear weapons. But the latest tests underline their growing nuclear capability.

The nuclear arms race between India and Pakistan has spawned a parallel missile race as each country seeks to develop medium and long-range missiles which might carry a nuclear warhead.

Only a few weeks ago Pakistan announced it had tried out a new missile at its own weapons testing site in Baluchistan.

But China - and especially India's fear of China's arsenal - is the prime factor driving India's weapons programmes. The fact that Pakistan's own missile and nuclear programmes have had considerable Chinese assistance only adds to India's concerns.

The Indian tests represent a significant set-back for the Clinton administration's non-proliferation policy. Washington has spectacularly failed to restrain either India or Pakistan's nuclear ambitions.

Washington is desperately seeking a lever it can use to try to bring pressure to bear. But Washington's own engagement with China adds another complex element to this difficult problem.