A top Pakistan Taliban commander has reaffirmed his group's ties to Al Qaeda, vowing to fight for imposition of Islamic law across the world, according to a video interview made available to Reuters.

The purported remarks by Wali-ur-Rehman, the commander of the Tehrik-e-Taliban Pakistan (TTP) in South Waziristan, underlined the persistent efforts of the group to raise its profile beyond Pakistan where it has carried out a deadly wave of attacks.

"Al Qaeda is a global organisation with branches spread all over the world, whether it is Arab countries, Europe, America or the subcontinent," Rehman said, sitting on the floor flanked by two bodyguards. A Kalashnikov lay at his feet.

"Many organisations are attached to it. We totally agree with their ideology and their agenda," he said.

"We will expand this war during the next 10 years," he added.

The interview was conducted by a Pakistani reporter in North Waziristan working for a foreign journalist, who gave the video exclusively to Reuters.

An expert on militant videos said that Rehman's comments show the TTP's growing global ambitions and that it should be taken seriously.

"Wali-ur-Rehman's repeated point that the TTP is interested in establishing shariah globally and not just in Pakistan underscores the threat posed by the TTP in the US and Europe," said Ben Venzke, CEO of IntelCenter in Washington, who confirmed the man speaking was Rehman.

"TTP can no longer be considered a localised threat actor."

On September 1, US prosecutors charged TTP leader Hakimullah Mehsud in a plot that killed seven CIA employees at an American base in Afghanistan last December.

Mehsud, believed to be hiding in the tribal areas of Pakistan, was also charged with conspiracy to kill Americans overseas and conspiracy to use a weapon of mass destruction.

The TTP was named a foreign terrorist organisation and $5 million bounties placed on Mehsud and Rehman.

Rehman, a close associate of Mehsud, told the interviewer that Osama bin Laden was alive, and continuing to direct operations.

"I can say with confidence and authenticity that he is alive and very active and keeps contacts with his close aides and gives them instructions," he says in the video.

US Secretary of State Hillary Clinton has said the US believes bin Laden and other al Qaeda leaders to be hiding in northwest Pakistan.

The TTP has made several threats against American and European targets, but the group has so far failed to carry out any overseas attacks. The attempt by Pakistan-American Faisal Shahzad to bomb Times Square who was linked to the TTP was the closest the group came to success.

In the 65-minute interview, Rehman mentions Pakistan's recent massive floods, and sends holiday greetings and sympathy to the people of Pakistan, suggesting the video was shot in August or early September.

The journalist said Rehman covers his head with a blanket when outside to evade the high-resolution cameras on the constantly circling unmanned US aerial drones, which have killed almost 100 militants in September alone. There was no way to confirm Rehman's security precautions.

During the interview, the journalist said, two drones orbited overhead, but did not attack.

The drones are a boon to his group, Rehman said, because the anger they fuelled helped bring more recruits to their cause.

"Because of these drone attacks, many people from around the world come to join us," he said. "On the one hand, we lost a lot because of these drone attacks. On the other hand we keep on receiving our sympathisers form different nations."

There has been media speculation in Britain that the recent upsurge in drone attacks in Pakistan was aimed at disrupting specific plots against European cities.

Rehman said there were "at least" 2,500 fighters in South Waziristan tying down the Pakistani Army, and about 18,000 TTP fighters across the whole country.

"We are sure, God willing, we would defeat the Pakistani army one day ... They have imposed an American war on us. Instead of conquering Kashmir, they are trying to conquer us."