Speaking by telephone from South Waziristan tribal region, where his forces have gathered strength in recent months, Haji Omar denied harbouring Al Qaeda members, but said he was organising attacks inside Afghanistan.

“There is no Al Qaeda here. There is only local Taleban, the Taleban of Waziristan,” Omar told Reuters.

“We do send mujahideen (holy warriors) to Afghanistan. We send mujahideen to areas where American and British troops are concentrated... we will continue our jihad against them. It is our religious obligation”.

Omar, along with a handful of other militant leaders in South Waziristan, signed a peace agreement with the army in 2004 and is not on any wanted list.

A senior security official in North West Frontier Province told Reuters on condition of anonymity that Omar was known to be recruiting fighters and sending them across the border.

Omar’s threat comes as the United States prepares to reduce its troop strength in Afghanistan to 16,500 from over 19,000. Britain is taking command of a NATO peacekeeping force next month and about 3,500 British troops are due to arrive in the volatile southern province of Helmand by the beginning of July.

Canada has about 2,300 troops in Kandahar, and the Netherlands is due to send up to 1,600 troops to Uruzgan province, another insurgent hotspot.

A veteran of the jihad, or holy war, against the Soviet occupation of Afghanistan in the 1980s, 45-year-old Omar also fought against American forces after the fall of the Taleban regime in Afghanistan in late 2001.

Omar says he met both Al Qaeda leader Osama bin Laden and Mullah Mohammad Omar, the leader of the Afghanistan’s Taleban movement before the September 11 attacks, but hasn’t seen them since.

He said the mujahideen had recovered from the disarray they fell into after the Taleban’s eviction.

The past year has been the bloodiest since the insurgency began against the Western-backed government of Afghanistan’s President Hamid Karzai.

US and Afghan officials often complain that Pakistan’s tribal lands are being used as a springboard for attacks inside Afghanistan, although the Pakistan army has deployed close to 80,000 troops on the border.