(Left: Soldiers of Pakistan's paramilitary force search incoming Afghan nationals at the Pakistan border, Feb. 16, 2010.)
The official (who spoke to CBS News) on condition of anonymity, said the arrest of Mullah Abdul Ghani Baradar was likely to produce "valuable information of the kind which will help both Pakistan and the United States aggressively deal with the Taliban."
Baradar's arrest — which took place several days ago but was revealed late Monday — was praised by Western diplomats and defense officials as a significant milestone in the war on terror.
The arrest came just weeks after an unprecedented news briefing by General Ashfaq Kiyani, Pakistan's army chief of staff, at which his signaled his intention to help build a new security regime for Afghanistan.
Specifically, Kiyani told select Western news organizations (including CBS News) that Pakistan had offered to help train Afghanistan's future military and its police. But his remarks were "meant to reassure the U.S. that Pakistan is now willing to become part of a new security arrangement for Afghanistan," said a Western defense official in Islamabad who spoke on Tuesday to CBS News on condition of anonymity.
The senior Pakistani security official who spoke to CBS News said Baradar's arrest was conducted in an operation carried out by Pakistan's ISI (Inter-Services Intelligence) counter espionage agency, while CIA operatives observed the arrest. "The interrogation is now being carried out jointly by the ISI and the CIA," added the security official.
News of the arrest comes at a critical time for the U.S. President Barack Obama, faced with a crucial year ahead as he tries to secure control of Afghanistan after recently ordering a surge in the presence of American troops, is seeking Pakistan's support for a more intense fight against Taliban militants in areas along the country's border with Afghanistan.
"Pakistan is a vital link for the U.S. in a carefully crafted chain to win the fight in Afghanistan and eventually withdraw its troops from there," said the Western defense official who spoke to CBS News.
However, the senior Pakistani security official said Pakistan's future support towards stabilizing Afghanistan will depend in part on the extent to which the U.S.-led global community accepts Pakistan's security challenges and helps to resolve them.
For Pakistan, the main challenges relates to its long-drawn conflict with India over the divided Himalayan state of Kashmir, as well as more recent Pakistani concerns over India moving to expand its influence in Afghanistan by widening its diplomatic presence there.
"Pakistan faces a continuing threat from India, both along our border with India as well as in Kashmir," said the Pakistani security official. "If Pakistan is expected by the global community to come fully on board, our security challenges have to be resolved."
While American and other Western officials remain concerned over Pakistan's links with hardline groups, they also increasingly look upon the country as a vital partner in the Afghan conflict, given the nation's past ties with the Taliban and other Islamic militant groups in and around Afghanistan.
By CBS News' Farhan Bokhari reporting from Islamabad.