When a suicide bomber posing as a Taliban envoy detonated his explosives at a meeting with the government's top negotiator last month, he appeared to have killed hopes of an Afghan peace process along with his human target.

But after over a month of puzzling about who exactly was behind the killing, which a Taliban spokesman has both claimed and denied, many of the Western countries with troops in Afghanistan have started cautiously trying to rekindle an effort that many see as the only real hope to end decades of war.

Violence is at the worst levels since the 2001 overthrow of the Taliban, and although NATO-led forces say they may be turning the tide, they have only three more years to do it.

All combat troops are due home by the end of 2014, and mounting bills and war weariness back home mean there is almost no chance foreign troops will be fighting on Afghan soil in significant numbers beyond that date.

U.S. Secretary of State Hillary Clinton said on a recent trip to Pakistan that the United States had held preliminary meetings with one of the main insurgent groups, the Haqqani network, and said she believed Pakistan had the capacity to encourage, to push, to squeeze them towards talks.

Her British allies seem equally sanguine about the chances eventually bringing everyone to the same table.

Every conflict ends in a negotiated solution, it's just a historical inevitability, Britain's ambassador to Kabul, William Patey, told Reuters in a recent interview.

He conceded that September's killing of the chairman of the high peace council, former President Burhanuddin Rabbani, meant that the current outlook for talks was pretty bleak, but said NATO-led forces should focus on military and diplomatic pressure to steer the Taliban towards negotiations in the longer term.

AFGHAN CONCERNS

The Afghan government and elite have been more circumspect. Rabbani's assassination confirmed the fears of those who had opposed talks and argue that the Taliban are irreconcilable.

It stoked anger and hatred, opening old wounds and deepening ethnic tensions in an already volatile country, where fear of civil war is growing. But for some, that unleashed tension was further evidence of the need to at least try talking.

President Hamid Karzai, a long-time proponent of trying to negotiate an end to violence, known to sometimes describe the Taliban as errant brothers, has not turned his back on talks although he has signalled a major change in approach.

He put his neighbour in the spotlight before Clinton arrived, suggesting that Pakistan-based insurgents are so closely controlled by their hosts that he must go directly to Islamabad to negotiate an end to the fighting.

Afghanistan's intelligence agency believes the plot to kill Rabbani originated in Pakistan and said the shadowy assassin was a Pakistani citizen, demanding answers from Islamabad.

Pakistan denies controlling the Taliban, or linked insurgent groups like the much-feared Haqqani network, but analysts say a settlement without Pakistan involved is doomed to fail.

I don't think we really know how open the Taliban are to talks, nor are we likely to find out unless we involve Pakistan directly in the negotiations, said Stephen Biddle of the Washington-based Council on Foreign Relations.

The Pakistanis have shown their ability to block any negotiation they're not happy with, and they are very unlikely to tolerate bilateral talks without them as a direct party.

WHAT'S IN IT FOR US?

The Taliban are now a reclusive, battle-hardened guerrilla group, who many believe have little incentive to talk; at present they are far stronger than Afghanistan's police and army, which are being rapidly expanded under NATO supervision.

The West wants out and the Taliban might now feel that they have the power, they don't need to negotiate and can just wait, said Shamila Chaudhary, a Eurasia Group analyst and former head of the U.S. National Security Council for Pakistan/Afghanistan.

But for the Taliban to come back, there'll be a lot of obstacles and resistance...maybe there are Taliban who are sick of fighting and want political roles, and therefore dialogue.

The fight would still likely be protracted and bitter, as groups that fought the Taliban in the 1990s or suffered under their rule start gearing up for a possible return to combat.

And current plans for a U.S.-Afghan strategic partnership envisage long-term bases on Afghan soil that could be used for bomber planes and drones. With their support, Afghan government forces could probably hold key cities for a long time, even if they lost their hold on the countryside.

Patey, Britain's ambassador, said that patience was not, on its own, enough to win the war.

The Taliban will realise one day that a strategy of simply waiting out the international community, waiting for the Afghans to devour themselves in some sort of civil conflict so they can march back from Kandahar to Kabul is a misplaced strategy.

BROKEN AGREEMENTS

Even if the Taliban do decide they want to cut a deal, Afghanistan has a history of broken agreements over 30 years of war, and mutual mistrust runs deep enough to put question-marks over any deal on paper.

Direct talks with the Taliban are believed have started late last year, but they have been plagued by setbacks and confusion.

Before Rabbani's killing, a previous Taliban envoy was found to have been a grocer from Pakistan who made off with tens of thousands of dollars.

Several meetings have been held between Rabbani's peace council and purported Taliban envoys in the past four months, but intelligence officials admit they are unable to verify whether they were legitimate representatives.

For now, getting the Afghan government, a factionalised Taliban, Pakistan, and the West to the table at a time of heightened U.S.-Pakistan tensions, rifts between Karzai and his foreign backers and Afghan feelings of disillusionment, anger and betrayal over Rabbani's death seems too much to ask.

It's just not possible in this kind of situation. There's no transparency in the Taliban and no one is speaking with Mullah Omar, said Ghulam Jelani Zwak, director of the Afghan Analytical and Advisory Centre in Kabul, referring to the leader of the Taliban.

It's clear there are groups in the Taliban who want to negotiate but the hurdle is Pakistan. So Pakistan should be involved, to see if it's really committed to the war on terror and to peace in Afghanistan.

(Editing by Emma Graham-Harrison)