by Ian Black

The United States and Britain are urging India and Pakistan to act with restraint and do nothing that could set back the recent thaw in their relations in the wake of the Mumbai terror attacks. But a direct public accusation by India yesterday that the perpetrators were linked to Pakistan risked rekindling tensions.

With signs of a growing rapprochement between the nuclear-armed neighbours linked to hopes for a more effective US and Nato-led military effort against al-Qaida and the Taliban in Afghanistan, the stakes for the south Asian region could hardly be higher, diplomats and analysts said.

"We are privately encouraging them not to do anything that could derail this process," a senior British official said.

Condoleezza Rice, the US secretary of state, is to discuss the crisis with foreign secretary David Miliband in London before a Nato ministerial meeting on Monday.

Whether by chance or design - some experts believe it was a goal of the terrorists - the Mumbai attacks came days after Ali Asif Zardari, the Pakistani president, made striking overtures: to withdraw his country's first-strike nuclear threat, sign the nuclear non-proliferation treaty, create an EU-style economic zone with India and allow visa-free travel.

Illustrating this progress, Pakistan's foreign minister, Shah Mahmood Qureshi, had just finished talks in Delhi with his Indian counterpart on terrorism, trade and visas when the terrorists struck.

But the fragility of the rapprochement was underlined too when Manmohan Singh, India's prime minister, said the attacks were probably masterminded by a group based in an unnamed "neighbouring country" - usually code for Pakistan.

India's foreign minister, Pranab Mukherjee, went further yesterday by saying that "initial evidence" showed "elements with links to Pakistan are involved".

International alarm at this finger-pointing was tempered by relief that Pakistan is behaving so helpfully. Zardari condemned the attacks and agreed yesterday to send the head of the powerful ISI intelligence agency, Lieutenant-General Ahmed Shujaa Pasha, to India to review evidence on the Mumbai atrocities.

Analysts said this suggested the Pakistan military was confident that no direct links will be revealed by India. Pakistan is keen to avoid a repeat of the near-war situation following the assault on the Indian parliament in December 2001.

But there were hints that the Pakistani authorities might acknowledge the existence of indirect links with terrorist groups: when Zardari telephoned Singh yesterday to again condemn the attacks, he said that "non-state actors" were responsible. "Non-state actors wanted to force upon the governments their own agenda but they must not be allowed to succeed," Zardari's office cited him as saying.

"Do not play politics into this issue," Qureshi warned. "This is a collective issue. We are facing a common enemy. We have to join hands to defeat this enemy."

The US state department said it, like Britain, was sending investigators to Mumbai to help the Indian authorities.The wider US concern, however, is about what one diplomat predicted could be "significant deterioration" in the process of Indo-Pakistani reconciliation. That has been boosted since Zardari, widower of the assassinated Benazir Bhutto, replaced Pervez Musharaf to become Pakistan's first civilian president since 1999.

Barack Obama, the US president-elect, has signalled that this will be a priority for him and for General David Petraeus, head of US central command. The aim is to persuade Pakistan to pay less attention to India and more to the al-Qaida and Taliban fighters in the border tribal areas.

On a visit to Afghanistan in July, Obama highlighted the regional aspect of the fight against the Taliban in that country and, increasingly, inside Pakistan. "A lot of what drives motivations on the Pakistan side of the border still has to do with their concerns and suspicions about India," he said. Pakistan continues to station the larger part of its army not on the Afghan border but along the line of control in Kashmir.

The two countries have fought three wars since independence in 1947 and nearly did so again in 2002 after the attack on India's parliament. Pakistan for years supported militants battling Indian forces in Kashmir but reined them in after the 9/11 attacks on the US. While seeking Pakistani cooperation in the "war on terror," the Bush administration also drew closer to India.