Media playback is unsupported on your device Media caption Pakistan's Prime Minister Yousuf Raza Gilani on his country's relationship with the US

Pakistan may continue its blocking of Nato convoys into Afghanistan for several weeks, Prime Minister Yousuf Raza Gilani has told the BBC.

Pakistan stopped the convoys in protest at US air strikes which killed 24 of its troops at two checkpoints on the Afghan border last month.

Mr Gilani refused to rule out closing Pakistan's airspace to the US.

He also denied rumours President Asif Ali Zardari had suffered a stroke and the army was trying to oust him.

Mr Gilani said Mr Zardari was making a rapid improvement in hospital in Dubai, but would need two weeks' rest before returning home.

Credibility gap

The air strikes on 26 November marked a low point in relations between Washington and Islamabad, which have long been strained by the US-led military campaign against militants in Afghanistan.

In a wide-ranging interview with the BBC, Mr Gilani said Pakistan and the US needed to trust each other better.

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"Yes there is a credibility gap, we are working together and still we don't trust each other," Mr Gilani said.

"I think we have to improve our relationship so that... we should have more confidence in each other."

Nato forces in Afghanistan rely significantly on overland supply routes from the Pakistani sea port of Karachi, which enter Afghanistan through the Khyber Pass.

Hundreds of lorries have been camped out next to border crossings, waiting for the crisis to blow over.

Asked about the state of health of Mr Zardari, Mr Gilani denied that the president had written a letter of resignation, as claimed by a source in Dubai.

"Why should he write?" asked Mr Gilani. "He has the backing and support of the entire parliament."

Dismissing speculation about a quiet coup, he said: "Rumours are rumours."

The Pakistani prime minister also denied a Pakistani Taliban claim that it was engaged in peace talks with his government.

But he added: "Whosoever surrenders and denounces violence, they are acceptable to us."

Base vacated

Nato has apologised for the air strikes, calling them a "tragic unintended incident".

In the aftermath, Pakistan also demanded the US leave the Shamsi air base in Balochistan.

Pakistani officials have confirmed that US forces have now vacated the base, meeting a deadline.

US officials could not be reached immediately for comment about the report.

Image caption US forces used Shamsi base for years

Shamsi was widely believed to have been used in covert CIA drone attacks against Taliban and al-Qaeda targets in north-west Pakistan's tribal areas bordering Afghanistan, but correspondents say it had not been used to launch drones for some time.

Vacating Shamsi is not expected to significantly curtail drone attacks in Pakistan, according to an Associated Press news agency report.

Mr Gilani also said he would investigate the blocking of the BBC's international news TV channel, BBC World News, by Pakistani cable television operators. Operators say the move is in response to a documentary broadcast by the channel entitled Secret Pakistan.

A BBC spokesperson said: "We welcome the prime minister's support of free speech and promise to investigate this ban. We call on the government to carry out an investigation rapidly and for BBC services to be restored in Pakistan.