"In the face of these ominous developments, which pose an immediate threat to our security, we cannot be expected to remain complacent," Sharif said in a letter to the Group of Eight (G8) industrialised states meeting in Birmingham, England. Foreign ministry secretary Shamshad Ahmad voiced Islamabad's disappointment at the G8 communique on India and said its failure to agree to US appeals for harsh economic sanctions showed that the group was divided.

"That only shows that they are divided, it's a very weak response, we hope that the sooner they realise their weaknesses the better it will be for regional stability and peace but also for the global peace and security," Ahmad said. The Birmingham communique said the Indian tests had affected relationships between New Delhi and eachcountry, condemned India and appealed for regional restraint. Ahmad said Pakistan had not taken a final decision but was keeping its options open. "I should say that there is no question of any renunciation of our options," he said.

"We have made it clear that we have never acted in haste and we will not act in haste or in madness and we will take a measured decision which will be determined by the compulsions of our national security," he said. The Pakistani premier, weighing domestic pressure to respond to India's boast of being a nuclear weapon state against potentially crippling sanctions, gave no clear hint as to whether his government would step over the nuclear threshold.

"We are... being asked to exercise restraint at an extremely critical juncture on matters involving national security and survival. I trust you would recognise and be receptive to Pakistan's legitimate need for self-defence," he wrote. Diplomats said Pakistan was looking to see whether G8 states would go further than the jointcommunique and take steps to isolate India and punish it harshly for its tests.

An India foreign ministry official said on Saturday that US sanctions would cost the Indian economy $1 billion a year. Sharif, under intense pressure from the United States and key economic backer Japan not to detonate a device, said India's "overt weaponisation is yet another manifestation of the highly irresponsible and reckless actions taken by India to escalate tensions in the region in recent weeks."

Delhi willing to discuss issue with Islamabad

India is ready and willing to discuss the nuclear issue with Pakistan anytime, Brajesh Mishra, principal secretary to the prime minister, has said.

"We do not want to dominate any other nation, nor do we want to attack anyone, but we must have a deterrent so that no one should dare attack us," Mishra told a programme on the Star TV. "We are ready to talk to Pakistan anytime," Mishra said when asked whether India would consider offering no-first-use option to Pakistan.However, he said he had no idea whether Islamabad was also ready to discuss the nuclear issue.