Relations between India and Pakistan were on a knife edge last night amid fears that Delhi’s response to the Mumbai attacks could undermine the Pakistani army’s campaign against Islamic militants on the frontier with Afghanistan.

Officials and analysts in the region believe that last week’s atrocities were designed to provoke a crisis, or even a war, between the nuclear-armed neighbours, diverting Islamabad’s attention from extremism in tribal areas bordering Afghanistan and thus relieving pressure on al-Qaeda, Taleban and other militants based there.

One analyst even described the attacks as a “pre-emptive strike” against Barack Obama’s strategy to put Pakistan and Afghanistan at the centre of US foreign policy.

The United States and its allies now face a balancing act in supporting India’s efforts to investigate the Mumbai attacks, without jeopardizing Pakistan’s crucial support for the Nato campaign in Afghanistan.

India’s government, facing an election by May, is under enormous pressure to respond to the attacks, which it believes was carried out by the Pakistani militant group Lashkar-e-Taiba, possibly with the help of al Qaeda.

Lashkar-e-Taiba was also blamed for an attack on the Indian parliament in December 2001, which prompted India and Pakistan to mass troops on each other’s border, almost triggering their fourth war since independence in 1947.

As the US announced Condoleezza Rice, the Secretary of State Condoleezza Rice would travel to India on Wednesday in a show of "solidarity," India's deputy interior minister said today all the attackers were from Pakistan.

"The terrorists who have been killed in these encounters in Mumbai in the last few days were of Pakistani origin," said Shakeel Ahmad.

However he stopped short of blaming the Pakistan government outright, telling the BBC: "We are not saying that it is sponsored by the Pakistan government."

The Indian government is now considering a range of responses, including suspending its five-year peace process with Pakistan, closing their border, stopping direct flights and sending troops to the frontier, according to Indian officials and analysts.

Pakistan’s government, meanwhile, has been rallying support in telephone calls to opposition politicians, as well as to officials in China, the United Arab Emirates and the EU.

It has also made it clear that if India again masses troops on the border, Pakistani forces would be diverted away from the tribal areas, allowing militants there to focus on Afghanistan.

“The next 48 hours are critical in determining how things unfold,” a top Pakistani security official told reporters. “We will not leave a single troop on the western border if we are threatened by India.”

His warning, highlighting the international implications of the Mumbai attacks, was clearly designed to encourage the United States and its allies to temper India’s response. The United States has forged a new strategic partnership with India since 2004, but has closer and older ties to Pakistan, a key Muslim partner in the War on Terror.

Pakistan has deployed more than 100,000 troops along its porous border with Afghanistan, where US and Nato forces are fighting against the Taleban, al Qaeda and other militants. Some 35,000 of those Pakistani troops are involved in the fight against al Qaeda and Taleban militants who have been sheltering in Pakistan’s northern tribal areas since late 2001.

Withdrawing those soldiers would undermine their progress, especially since Pakistan launched its biggest offensive to date against the militants in the tribal region of Bajaur in September.

“We are highly encouraged by the Pakistani military progress,” said Colonel Gregg Julian, a U.S. military spokesman. “It is creating pressure on al Qaeda from two sides and it is getting very difficult for them right now. We would hope that they are able to keep up that pressure.”

Pakistani officials and analysts said that withdrawing troops would also benefit local militant groups like Lashkar-e-Taiba and Jaish-e-Mohammed. “The withdrawal of troops will give a huge space to the militants,” said Hasan Askari Rizvi, a Pakistani defence analyst and former professor at Punjab University.

“The main objective of the militants involved in the Mumbai attack was to destablise the region… They will thrive in the event of war between the two countries [India and Pakistan].”

The two groups were originally founded by Pakistan’s Inter-Services Intelligence agency as deniable proxies to be sent to fight Indian forces in the disputed region of Kashmir. They have been blamed for numerous attacks on Indian targets.

However, Western intelligence agencies have recently perceived a growing nexus between these and other, militant groups such as the Pakistani Taleban and al Qaeda. In June, it was reported that some 300 militant leaders from a number groups including Lashkar-e-Taiba and Jaish-e-Mohammad met in the Pakistani garrison city of Rawalpindi.

There they reportedly agreed that while the Kashmir struggle remained important, their primary focus should be the fight against international forces in Afghanistan.

Just a few weeks later, nine US soldiers were killed in an attack on a combat outpost at Wanat in the Afghan border province of Nuristan that displayed unusual military competence. Intelligence reports subsequently assessed that the assault included a significant Lashkar-e-Taiba element, as well as al Qaeda fighters.

The growing relationship between al Qaeda and Lashkar-e-Taiba may explain the scale and sophistication of the Bombay attacks, said Dr Kanchan Lakshman of the South Asia Terrorism Portal. “It would also suggest why they targeted Americans, British and Israelis,” he said.

He added that he had heard from an Indian intelligence official that the Mumbai attack had been funded by Saudi money, again suggesting an al Qaeda link.

Other Indian analysts said the attack appeared to be an attempt to undermine US policy towards India, Pakistan and Afghanistan.

“There’s a lot of clamour for action against Pakistan from India,” Pratap Bhanu Mehta, the head of the Centre for Policy Research. “This attack was not just an attempt to scuttle India’s peace process with Pakistan. It was in many ways a pre-emptive strike against [Barack] Obama’s strategy for the region.”

The U.S. President elect has proposed increasing troop levels in Afghanistan and stepping up the pressure on Pakistan to attack militants on its territory. In exchange, he has suggested appointing an special envoy to help resolve Pakistan’s territorial dispute with India over Kashmir.

A crisis in India-Pakistan relations would scupper both plans.

Doctor Antonio Giustozzi, an expert on Afghanistan at the London School of Economics, said Washington could weather such a crisis, but concurred on the militants’ aims.

“I think that the terrorists have made a calculation that aims to worsen relations between India and Pakistan and embarrass the Pakistan government, in the hope that the Indians make an uncontrolled response,” he said.

That, he said, would “strengthen the militants’ hand and compromise the campaign by Islamabad against extremists by diverting troops back to the Indian border.”

Times Recommends

• LA profits from Michael Jackson stimulus
• Berlusconi's absent wife causes G8 headache
• Chimps that took a punishing step for Man