Pakistan is to release its most senior Afghan Taliban detainee, Abdul Ghani Baradar, a former military chief often described as the insurgents' ex-second in command, officials said Tuesday.

The Afghan government has long demanded that Islamabad free Baradar, whose arrest in January 2010 saw Pakistan accused of sabotaging initiatives to bring peace in war-torn Afghanistan.

His release would bring to 34 the number of Taliban detainees that Pakistan has released since last year, in what Afghan officials hope will encourage peace talks with the insurgents.

There has been little evidence, however, that the releases have had a positive effect on stalled talks, and Baradar's influence has been debated after years away from the battlefield.

"Pakistan has decided in principle to release Mullah Baradar," Sartaj Aziz, advisor to the prime minister on national security and foreign affairs, told AFP.

Aziz said Baradar would not be handed over to the government in Afghanistan, but was "likely to be released this month".

Pakistani foreign ministry spokesman Aizaz Ahmad Chaudhry confirmed to AFP that the decision had been taken to release Baradar "at an appropriate time".

The announcement came two weeks after Afghan President Hamid Karzai visited Pakistan for talks with new Prime Minister Nawaz Sharif, at which Baradar's release was again requested.

A member of Afghanistan's High Peace Council, set up to coordinate peace efforts, welcomed the prospective release but called on Pakistan to coordinate his release with them.

"We hope that they work in coordination with Afghanistan's High Peace Council," said Mohammad Ismail Qasemyar.

Karzai at the end of August asked Pakistan to help open direct dialogue between his government and the Taliban. He was infuriated by the opening in June of a Taliban office in Qatar, considered a precursor towards talks with US officials.

Elements of the Pakistani state are widely accused of funding, controlling and sheltering the Taliban. Islamabad says publicly it will do anything to stop the fighting in Afghanistan.

But analysts doubt Pakistan has the influence to force the Taliban to the negotiating table and the insurgents have publicly refused all contact with Karzai's government.

Karzai's office said it would respond later to Baradar's prospective release, and Taliban spokesman Zabiullah Mujahid told AFP the militia was assessing the situation.

Afghan officials believe prisoner releases can encourage former detainees to talk to the Kabul government, although several prisoners are understood to have returned to the battlefield.

Born in the southern Afghan province of Uruzgan, Baradar fought in the war -- covertly backed by the United States and Pakistan -- to expel Soviet troops from Afghanistan in the 1980s.

When the Taliban rose to power in 1996, Baradar's friendship with supreme leader Mullah Omar made him deputy defence minister.

After the Taliban government was toppled by the US-led invasion in 2001, hundreds of Taliban hardliners are believed to have fled over the border to Pakistan.

Although little is known about Baradar's more recent activity, Interpol has said that he had been a member of the Taliban's so-called Quetta Shura leadership since May 2007.

He was arrested in Pakistan's southern port city of Karachi, reportedly in a secret raid by CIA and Pakistani agents, an operation that was described as a huge blow to the group.

At the time, Baradar was reported to have been second or third-in-command of the Quetta Shura.

The New York Times -- which broke the story of Baradar's arrest -- said the commander was a close associate of Al-Qaeda leader Osama bin Laden before the September 11 attacks.

In early 2010, the Afghan government and the former UN envoy to Afghanistan said his detention had adversely affected efforts to talk to the insurgents.