LONDON When Defense Secretary Robert Gates said last week al Qaeda and its allies might try to provoke a conflict between India and Pakistan, he articulated what many see as the biggest risk to U.S. plans for the region.
A major attack on India by Islamist militants could lead to retaliation by a country still bruised by last year's assault on Mumbai, further destabilizing nuclear-armed Pakistan.
"The Pakistanis are really frustrated. They keep being told to 'do more'," said Kamran Bokhari at U.S. think-tank Stratfor.
He said Pakistan was worried about the possibility of another militant attack on India but unsure how to prevent it.
Pakistan is already fighting militants who attacked its military headquarters in October and last week killed at least 40 people in a nearby mosque used by the army.
"When they can't guarantee there will be no attacks in their own country, they can't guarantee India won't be attacked."
India, angry at Pakistan's refusal to act against the Lashkar-e-Taiba militant group blamed for killing 166 people in the Mumbai attacks, has rejected calls for talks and suggested it could even retaliate were there to be another major attack on Indian soil.
As a result, tension is at its worst since 2002 when one million men were mobilized on the border after a December 2001 attack on the Indian parliament by Pakistan-based militants.
"It's not as bad as 2002," said Praveen Swami, a defense expert at the newspaper The Hindu. "But it is the worst it has been since then."
It is a situation which al Qaeda may try to exploit.
Defense Secretary Gates told a U.S. Senate hearing last week al Qaeda was helping Lashkar-e-Taiba plan attacks in India, "clearly with the idea of provoking a conflict between India and Pakistan that would destabilize Pakistan."
Indian Prime Minister Manmohan Singh has said war is not an option, and nobody expects a repeat of 2001-2002.
"We are not going to see that kind of mobilization again," said one Indian defense analyst. However, some have raised the possibility of "surgical" strikes against militant camps India says are still operating in Pakistani Kashmir. "The difficulty is in signaling this is not the start of a full war," he said.
The Pakistani army, taunted by the Taliban for fighting its own people and killing fellow Muslims, would have no choice but to respond against even limited strikes by India.
"There is no way they could not respond," said Bokhari, adding that the army would otherwise lose all credibility.
While the U.N. Security Council would be expected to step in quickly to stop any conflict from escalating, it would still leave U.S. plans for Afghanistan and Pakistan in disarray.
Immediately after Mumbai, India turned to the United States to put pressure on Pakistan to dismantle the Lashkar-e-Taiba.
Initial hopes in India that Pakistan might act, combined with the return to power in May of Prime Minister Singh in a general election, paved the way for talks between the two countries on the sidelines of international meetings.
The thaw let Pakistan redeploy some troops from its border with India to its western frontier with Afghanistan.
The two countries have since descended into mutual recriminations, with Pakistan accusing India of using its growing presence in Afghanistan to stir up trouble in its Baluchistan province, an allegation New Delhi denies.
Analysts say intelligence reports that Lashkar-e-Taiba, once nurtured by Pakistan's Inter-Services Intelligence to fight in Kashmir, continues to plan fresh attacks on India has soured the mood further.
Pakistan is seen as unwilling to act against Lashkar, one of the few militant groups not believed to have targeted Pakistan itself, when it faces so many other problems.
That has closed off nearly every avenue for talks, including the informal diplomacy that in the past has cushioned the effects of crises in relations, such as immediately after Mumbai.
Some analysts see the deadlock as a sign of a failure of U.S. diplomacy and evidence of deep divisions within the U.S. administration over how to handle Pakistan.
Ever since India and Pakistan conducted nuclear tests in 1998, the United States has played unofficial peace broker.
While it has quietly encouraged India and Pakistan to talk, it seems to have no clear idea how to end the stalemate.
"There is no real diplomacy going on," said Tarak Barkawi, a defense expert at Britain's Cambridge University. Without diplomacy, Washington had little to offer Pakistan except widening Predator drone attacks.
At least in Afghanistan, U.S. troops could try to provide security and economic development. "All we can do in Pakistan is blow things up ... blow things up from afar," he said. "The whole presence of America in Pakistan is a destructive one."
Nor does it have much to offer the Indian government, reluctant to start a conflict which might aggravate instability in its neighbor and determined to see off the threat it believes is posed by the Lashkar-e-Taiba.
"I think they are very worried about Pakistan," said Swami. "But they don't know what to do about it."
(For a FACTBOX on the Lashkar-e-Taiba, double-click on
(For more Reuters coverage of Afghanistan and Pakistan, see: here)
(Editing by Andrew Dobbie)