At last Pakistan and the United States appear to be genuinely co-operating in the battle against the Taleban and al-Qaeda militants in the mountainous tribal areas along the porous border with Afghanistan.

Pakistan has finally accepted that it has to send its army into South Waziristan to kill or capture Baitullah Mehsud, the leader of the Taleban in Pakistan and the main al Qaeda “facilitator” in the region.

The US has belatedly acknowledged that it needs to deploy its CIA drones against Mehsud, instead of concentrating solely on al-Qaeda figures seen as a bigger threat to America.

A drone strike on Tuesday that narrowly missed Mehsud but killed dozens of his men was probably carried out at Pakistan’s request and based on its intelligence — although the Government still publicly opposes such attacks. The strike also helped to suppress persistent rumours here that the United States is somehow supporting the militant leader as part of a conspiracy to split the country and capture its nuclear weapons.

The question is how long this apparent period of co-operation — and relative stability on the domestic political front — will last. US and British officials would like the army to attack not just Mehsud but other militant leaders in South Waziristan and North Waziristan — al-Qaeda’s main sanctuary and a possible hiding place of Osama bin Laden.

They would like the army to stay in the North West as long as it takes to strengthen the local police, improve local governance, and pour in millions of pounds of civilian aid to help to prevent the Taleban from returning. They would also like Pakistan to take stronger action against the militants blamed for last year’s attack on Mumbai so that India will resume frozen peace talks over Kashmir, seen as key to President Obama’s “AfPak” strategy.

But the army has made it clear that its aim is to kill or capture Mehsud, whom it blames for recent suicide bombings and for the assassination of Benazir Bhutto, the former Prime Minister, in 2007. It is understood to be negotiating a deal with two other Taleban leaders in the region — Mullah Nazir in South Waziristan and Hafiz Gul Bahadur in North Waziristan — to make sure they do not come to Mehsud’s aid.

Pakistan’s Government has yet to present a detailed plan for improving security and governance in North West Frontier Province, and establishing control over the Federally Administered Tribal Areas. The problem is that President Zardari lacks the political strength to push through the sweeping political reforms required in the area, or to grant India the concessions it is demanding to resume the peace process.

Moving too far or too fast could leave him vulnerable to attacks from Nawaz Sharif, the former Prime Minister who heads the opposition Pakistan Muslim League (N) party and remains determined to lead the country again. Mr Sharif has been remarkably quiet since leading a lawyers’ march against the government in March — and his aides like to say this is because of a deal with Washington under which he will return to power in the near future.

Western diplomats say there is no such deal. But they are acutely aware that the current window of opportunity to tackle the militants in the North West without risking a public backlash could slam shut as suddenly as it opened.

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