Pakistan has sought U.S. help to capture an Arab Al Qaeda terrorist who allegedly masterminded the foiled plot to blow up trans-Atlantic jetliners and operates out of Afghanistan's eastern mountains where hundreds of American troops are based, an intelligence official said Friday.

Pakistani authorities have passed details regarding the Al Qaeda member to the American military, including his whereabouts in the remote Nuristan and Kunar provinces on the Pakistan border, through which hundreds of militants and locals routinely cross, the official said.

The official, who spoke on condition of anonymity due to the sensitive nature of the investigation, declined to reveal the Al Qaeda operative's name or nationality.

But he allegedly exchanged messages carried by a courier with detained British national Rashid Rauf, who is being interrogated by Pakistani authorities in connection with the plot that was smashed last week with at least 30 people arrested in both Britain and Pakistan, the official said.

The wanted Al Qaeda operative is a close aide to Egyptian-born Al Qaeda No. 2 Ayman al-Zawahiri, the official said. Detained terror suspects have told interrogators that al-Zawahiri likely approved the plan to blow up passenger planes leaving London for the United States by detonating disguised liquid explosives carried onboard in hand luggage.

A U.S. military spokesman in Afghanistan said Pakistan routinely shares terror-related information with American counterparts, but he could not comment on whether Islamabad had notified U.S. authorities about the Al Qaeda mastermind.

Hundreds of American troops from the 10th Mountain Division, out of Fort Drum, New York, are based in the Kunar and Nuristan provinces hunting Al Qaeda terrorists and militants allied to the Taliban and wanted Afghan warlord Gulbuddin Hekmatyar.

But the mountainous terrain, porous borders and limited presence of security forces make it difficult for American and Afghan authorities on one side of the border and Pakistanis on the other to seal the frontier.

Rauf, who was arrested in eastern Pakistan days before the plot was foiled, is regarded as a key figure in the attack plan. He left Britain in 2002 after becoming a suspect in his uncle's killing. Officials here have alleged that he recruited would-be bombers to take part in a large-scale attack to mark the Sept. 11, 2001 terrorist strikes.

Authorities here have also accused Rauf of once belonging to the banned Pakistani militant group, Jaish-e-Mohammed, but said he later aligned himself with Al Qaeda members in Pakistan and Afghanistan.

In Bhawalpur, a Jaish-e-Mohammed stronghold in eastern Punjab province where Rauf was arrested, police sealed his house and his wife and two children have moved to an undisclosed location to escape the intense media attention, an Associated Press reporter said.

Rauf's father, Abdul Rauf, who flew to Pakistan shortly before his son's arrest to attend a wedding, is also being questioned by investigators, but he has not been charged and will be allowed to return to Britain at the end of the interrogation, the intelligence official said.

Afghan officials have rejected Pakistani claims that militants in Afghanistan played a role in the London terror plot and instead blamed Pakistan for not doing enough to crack down on terrorists operating on its soil.

Rauf is among at least seven people detained in Pakistan in a roundup that helped foil the plot. Some 23 people have also been detained in Britain, including Rauf's 22-year-old brother, Tayib.

British investigators are in Islamabad working closely on the investigation with Pakistani counterparts. British and Pakistani officials have also been discussing the prospect of extraditing Rauf to Britain.

But Pakistan's Interior Ministry spokesman said any imminent extradition was unlikely.

"I think extradition at this point of time is not under consideration because the investigation is still ongoing," said Brig. Javed Iqbal Cheema. "But we are not ruling it out."

Investigators were also looking into how the plot may have been financed and are focussing on leads outside of Pakistan, Foreign Ministry spokeswoman Tasnim Aslam said without elaborating. She rejected reports that Islamic charities funneled funds to militants here for use in the plot.

The Afghan-Pakistan border has long provided sanctuary for Islamic militants, including al-Zawahiri and Al Qaeda leader Usama bin Laden.