The high-level talks, aimed at reviewing progress in the slow-moving peace process, were thrown into doubt after Indian authorities said Pakistani-based Islamic militants could be responsible for Tuesday's blasts.

"We will take a decision on this at an appropriate time," Indian foreign secretary Shyam Saran said of the talks which were tentatively slated for Thursday.

"Whether we like it or not, this (attack) becomes a question mark over the (peace) process. As a result of these terrible terrorist incidents, it is becoming difficult to take this process forward," Saran told reporters.

His statement came after Indian Prime Minister Manmohan Singh said Friday that the Mumbai attackers had support from "elements across the border" in a reference to Pakistan.

Before the blasts, Islamabad confirmed it would take part in talks between the foreign secretaries of two nuclear-armed neighbours. But after the blasts Indian officials said they had not officially confirmed the date.

Singh warned that the peace process could be harmed if Pakistan did not live up to a promise to curb "terrorism" directed against Indian targets.

Pakistan has rejected Singh's claims as "unsubstantiated" and said peace talks "must be continued and carried forward". It also said it has taken action to rein in militants operating on its soil.

New Delhi accuses Pakistan of training Islamist rebels fighting Indian rule in Kashmir, split between the two and claimed in full by both, a charge denied by Islamabad. The Himalayan region has sparked two of their three wars.

India blames Pakistan-based militant outfit Lashkar-e-Taiba, banned by both the countries, for a number of attacks in India, including one on its parliament in 2001 which nearly brought the neighbours to war.

Lashkar-e-Taiba has emerged as a key suspect in the Mumbai train bombings, although the outfit has denied responsibility for the attacks.

The peace talks, launched in January 2004, have led to restored transport links and increased trade. But the neighbours have made no headway on Kashmir, at the core of their nearly six decades of hostility.

Saran said dates for the talks had not been decided, and added that India was "very much committed to pursuing a policy of peace and friendship with Pakistan."

India's Congress-led government has come under strong pressure from local media to take a tougher stand towards Pakistan following the bombings.

"If (Pakistani President Pervez) Musharraf is not willing or is unable to deliver an end to cross-border terrorism, the government could only conclude it is no longer possible to do business with him," said Indian Express foreign affairs analyst C. Raja Mohan.

In a sign of a changing mood towards Pakistan, two Indian parliamentarians cancelled their planned trip to Islamabad to attend a Commonwealth workshop on women and development beginning on Sunday.

"When we go to any meeting in Pakistan, we are going as MPs. It won't be very fit to go right now ... with the present circumstances," legislator Sandeep Dikshit of the Congress party told CNN-IBN TV network.

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