There is an implicit threat in the Chinese statement underlining that India's and Pakistan's recent nuclear tests have a strategic significance way beyond their own borders.

China last tested a nuclear device in July 1996. It then signed up to the Comprehensive Test Ban Treaty, which - though it has not yet entered into force - establishes a powerful international norm against testing.

China's suggestion that the Treaty allows countries to resume testing if they believe it to be in their supreme national interest is true as far as it goes - but then all treaties can be broken should a country feel that the treaty regime no longer adds to its own security.

And if a declared nuclear weapons state were to withdraw from the test ban regime the consequences would be very serious. The whole treaty would be undermined.

China is especially concerned because some of the more strident Indian statements have pointedly declared that India's nuclear deterrent is directed more at China than Pakistan.

India wants to be counted as a major regional player and sees nuclear deterrence as one of the trappings of this position.

China is signalling that urgent steps must be taken to constrain the nuclear arms race between India and Pakistan.