Pakistan freed the Afghan Taliban’s former deputy leader on Saturday after years of detention in a move that many officials in Islamabad and Kabul hope will aid Afghanistan’s struggling peace process.

But others doubt Mullah Abdul Ghani Baradar will do much good, and the United States, which opposed his release, is worried he could return to the battlefield. That could give the Taliban in Afghanistan a boost at a time when the U.S. is drawing down its troops and increasingly relying on Afghan forces to fight insurgents.

Kabul has demanded Islamabad free Baradar ever since he was arrested in a joint raid in the southern Pakistani city of Karachi in 2010 after holding secret peace talks with the Afghan government. Pakistan resisted for years, exacerbating already tense relations with neighboring Afghanistan.

Pakistan’s change of heart came amid a renewed push to help strike a peace deal between the Taliban and the Afghan government before the U.S. withdraws most of its combat troops by 2014. Pakistan is increasingly worried that further instability in Afghanistan could make it more difficult to fight Islamic militants at home.

Baradar was released Saturday morning, said Pakistani Foreign Ministry spokesman Aizaz Ahmad Chaudhry without providing further details, including where the prisoner was held.

Baradar will remain in Pakistan after his release and will be provided with tight security, said Pakistani intelligence and security officials, speaking on condition of anonymity.

He will be free to meet with anyone he chooses, they said. Presumably that could include talks with Taliban commanders and Afghan officials to aid the peace effort.

Baradar’s family, which lives in Karachi, had not heard from him by Saturday evening, said a family friend.

Afghan President Hamid Karzai’s spokesman welcomed Baradar’s release and urged Pakistan to ensure that he is accessible to the High Peace Council, which has been tasked by the Afghan government to negotiate with the Taliban.

“We want Mullah Baradar to be safe and accessible with reachable address, so he can contribute to the Afghan peace process,” spokesman Aimal Faizi said in a statement.

Baradar, who is around 50 years old, was one of the founding members of the Taliban along with the group’s leader Mullah Omar. He served as a senior military leader and deputy defense minister after the Taliban seized control of Afghanistan in 1996.

Wakil Ahmad Muttawakil, who served as foreign minister when the Taliban ruled Afghanistan, also hailed Baradar’s release and cautioned Pakistan not to try to control his movements now that he is free.

“They also have to allow him contact with Taliban leaders and for him to be useful for peace in Afghanistan,” Muttawakil said.

Not everyone agreed that Baradar’s release would contribute to peace, saying his long imprisonment had robbed him of both his influence and status in the Taliban.

“This is a very, very meager step. It will not bring peace,” said Mohammad Daoud Sultanzai, an Afghan political commentator and talk show host. “He doesn’t have an importance among the Taliban leadership, or any other leadership that would be able to deliver anything with authority.”

Pakistan has released at least 33 Taliban prisoners over the last year at the Afghan government’s request in an attempt to boost peace negotiations between the insurgents and Kabul. But there is no sign that the previous releases have helped peace talks, and some of the prisoners are believed to have returned to the fight against the Afghan government.