"In this instance, India is on the wrong side of history," Clinton said in his weekly radio address. "India has pursued this course at a time when most nations are working hard to leave the terror of the nuclear age behind."

He urged India to sign the Comprehensive Test Ban Treaty (CTBT), and renewed calls for the US Senate to ratify the agreement, which has languished in the face of opposition from key Republicans since he submitted it in September, 1997.

"Now it's all the more important that the Senate act quickly, this year, so that we can increase the pressure on, and isolation of, other nations that may be considering their own nuclear test explosions," he said.

Clinton recorded the address late on Friday, shortly after he and other leaders meeting for the Group ofEight summit in Birmingham, England, jointly condemned the testing and urged India to adhere to agreements controlling nuclear weapons.

India conducted a total of five nuclear test explosions this week. The action provoked wide international condemnation, and prompted neighbouring Pakistan to consider conducting a test of its own.

But few countries joined the United States in swiftly imposing sanctions against India.

In the G8 statement on Friday, the leaders vowed unspecified individual actions to make clear their displeasure with India's testing. They also urged Pakistan to show "maximum restraint".

Asked on Saturday morning whether the statement about India was strong enough, in the absence of sanctions, to persuade Pakistan to refrain from testing, Clinton said: "I don't know, but I hope so."

Deputy US secretary of state Strobe Talbott was to arrive in England to brief Clinton following a mission to Pakistan to try to persuade it not to test. In his radio address, Clinton said the test bantreaty, which bans all nuclear explosions, makes it more difficult for nuclear powers to develop advanced weapons and for non-nuclear states to acquire them. The treaty has been signed by 149 nations.

Clinton said treaty provisions for a network of sensors and inspections would discourage countries from cheating.