Tensions between Pakistan and the United States came to the fore last night when Yousuf Raza Gilani, the new Pakistani Prime Minister, met President Bush and warned him not to launch "unilateral" strikes on Pakistani soil.

The meeting came just hours after Pakistani security officials said that a suspected US missile strike on a village in Pakistan's northern tribal areas might have killed an al-Qaeda chemical and biological weapons expert.

Mr Gilani, who has been under pressure to do more to combat al-Qaeda and Taleban militants in Pakistan, told reporters after his meeting at the White House that Pakistan was committed to fighting extremists.

"We are committed to fight against those extremists and terrorists who are destroying and making the world not safe," he said.

"This is our own war; this is a war which is against Pakistan."

He went further in an interview with CNN a few hours later, when he was asked about the suspected US missile strike earlier in the day.

Mr Gilani said he had told Mr Bush that "unilaterally it should not be done".

If the missile strike was proven to have been a US operation, it would be a violation of Pakistani sovereignty, he said.

"Basically Americans are a little impatient. Therefore in the future I think we'll have more co-operation on the intelligence side and we'll do the job ourselves," he said.

Pakistan has been a key US ally in the War on Terror ever since the September 11, 2001 attacks and has received an estimated $10 billion in mostly military aid in return over the last six years.

But Mr Gilani's remarks revealed the growing tension between Islamabad and Washington over how to tackle the militants, many of whom have been sheltering in northern Pakistan since being driven out of Afghanistan by a US-led invasion in late 2001.

Concerned about mounting Nato casualties in Afghanistan, the United States has been pressing Pakistan for months to take more direct action to prevent the militants from making incursions over the Afghan border.

But Pakistan is reluctant to anger its mostly Muslim population and to complicate relations with the independence-minded Pashtun tribesmen who populate the frontier with Afghanistan.

Since coming to power in February elections, the new Pakistani government has negotiated ceasefire agreements with the militants that US officials fear will only give them time to regroup.

So in recent months, the United States has increased the frequency of its missile attacks on militant targets in Pakistan -- many of them using unmanned Predator drones.

Most have been with the tacit permission of Islamabad, but Pakistani officials complain that several have been conducted without their prior knowledge.

Ties were further strained by a US airstrike last month that killed 11 Pakistani border troops.

Mr Bush stressed after his meeting with Mr Gilani that the United States respected Pakistan's sovereignty.

"The US, I repeat, respects the sovereignty of this democracy. And we also appreciate the Prime Minister's strong words against the extremists and terrorists who not only would do us harm but have harmed people inside, in Pakistan," Mr Bush said.

Mr Bush called Pakistan a "strong ally" and said he had received a "strong commitment" from Mr Gilani that Pakistan would try "as best as possible" to prevent militants from crossing from Pakistan into Afghanistan.

Meanwhile, Pakistani security officials were still trying to check reports that the suspected U.S. missile strike had killed Abu Khabab al-Masri, also known as Midhat Mursi al-Sayid Umar.

Al-Madri was a 55-year-old Egyptian chemist regarded as one of al-Qaeda's top bomb makers and had a $5 million bounty on his head. Similar reports in 2006 turned out to be unfounded.

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