The Afghan government has been holding secret talks for months with a Taliban group linked to al Qaida, a source said.
A member of the Afghan parliament who did not want to be identified said President Hamid Karzai's government had been in direct contact with Jalaludin Haqqani, the ageing leader of the Haqqani network, which is based in Pakistan and is believed to have close ties to Pakistan's intelligence service.
Confirmation of talks with the Haqqani network would indicate that negotiations are being held with more than a handful of disaffected low- to mid-level insurgents as the West seeks an end to the more than nine-year-old war.
While sceptical in the past, the US last week expressed support for the Afghan government's efforts to talk with senior members of the Taliban.
Mr Karzai, meanwhile, has asked Pakistan to hand over 31 Taliban figures who have been detained in the neighbouring country, including Mullah Abdul Ghani Baradar, the Afghan Taliban's number two leader who was arrested in February in a joint raid with the CIA.
The Taliban released a statement on Tuesday saying no top leaders of the Taliban, known as the Islamic Emirate of Afghanistan, have been talking to the Afghan government.
US officials have long said they did not expect the Taliban - the hard-line Islamic movement that harboured Osama bin Laden - to talk peace as long as the militants believed they were winning. The Taliban's refusal to hand over bin Laden after the September 11 attacks triggered the Afghan war.
That stance changed publicly last week when US Defence Secretary Robert Gates and Secretary of State Hillary Clinton backed exploratory talks between the Afghan government and the militants.
Top Nato commander General David Petraeus confirmed that coalition forces were providing safe passage to some top Taliban leaders who were talking to the Afghan government.
The new acceptance of reconciliation could be seen as an admission that the war is going badly. Or it may reflect the view of US military commanders that Nato troops have damaged the insurgency following the surge of more than 30,000 US forces ordered by President Barack Obama.