KABUL: The head of the Nato-led force in Afghanistan has vowed that the long-delayed transfer of detainees from US to Afghan control will not take place if they pose a threat to international troops.

The transfer of a final group of detainees at Bagram jail has been a cause of friction between President Hamid Karzai and the coalition, and a handover ceremony was abruptly cancelled on Saturday.

“There's probably a difference of opinion. We certainly don't have anyone in the detention facility that we think doesn't deserve to be there,” General Joseph Dunford, commander of Nato forces, said.

“If there's a threat to the force, we will not conduct the transfer,” he said in a pool interview late Saturday. “If there are people that need to be detained, we will make sure they are detained.” Dunford's stance is likely to anger Karzai, who on Saturday insisted that the controversial Bagram jail, 50 kilometres (30 miles) north of Kabul, was put in Afghan control within days.

“President Karzai stressed that all efforts must be made to make sure the handover happens this week and that Afghanistan's sovereignty comes into full exercise,” a statement from his office said.

Last September, the United States passed the Afghan authorities control of more than 3,000 detainees at Bagram.

But the Americans continued to guard 50 foreigners not covered by the agreement and hundreds of Afghans arrested since the transfer deal was signed in March 2012.

Kabul made control of the prison a condition for signing a long-term agreement and a possible legal immunity deal that would allow some US troops to remain in the country after foreign combat forces withdraw next year.

US officials suggest that some released detainees have returned to the battlefield, and there are fears that the government is freeing suspected militants to help kick-start peace talks with the Taliban.

Karzai said this week that after the transfer he would order the release of all innocent detainees, even though he expected to face criticism for his actions.

Saturday's ceremony was cancelled on the same day that a suicide bomber killed nine people in Kabul during a visit by new US Defense Secretary Chuck Hagel.