The Afghan government will not take part in peace talks with the Taliban unless the process is "Afghan-led", President Hamid Karzai said Wednesday, a day after the US said it would talk with the Taliban in their new office in Qatar.

Karzai said the opening of the Taliban office contradicted earlier US security guarantees to his government, BBC reported.

He said that in protest he would suspend talks with the US on its presence after NATO troops leave Afghanistan in 2014.

Meanwhile, four US soldiers died in a Taliban attack at the Bagram air base, the largest military base for US troops in Afghanistan.

A statement from Karzai's office said Afghan negotiators would stay away from the Qatar talks until "foreign powers" allowed the process to be run by Afghans.

"Unless the peace process is 'Afghanised', the High Peace Council is not attending the Taliban Qatar talks," BBC quoted the statement as saying.

The High Peace Council was set up by the government to lead peace efforts with the Taliban.

The fact that the Taliban opened a political office in Qatari capital Doha was "totally contradictory to the guarantees that were made by the US to Afghanistan", Karzai's statement added.

The office opened Tuesday, just hours after the US announced that it would begin direct talks with the outfit -- and on the same day that NATO handed over the security for the whole of the country to the Afghan government for the first time since the Taliban were ousted in 2001.

The White House demanded two preconditions for the talks -- that the Taliban make a statement supporting a peace process, and that it opposes the use of Afghan soil to threaten other countries. The Taliban accepted.

A ceasefire is not part of the preliminary negotiations, BBC said.

US President Barack Obama Wednesday said he always expected "friction" at the Afghan peace talks.

"My hope is that despite those challenges the process will proceed," Obama said during an official visit to Berlin.

"Ultimately we're going to need to see Afghans talking to Afghans about how they can move forward and end the cycle of violence, so they can start actually building their country," Obama said.

Afghanistan's National Security Council confirmed that Karzai suspended the fourth round of the bilateral security agreement talks.

"There is a contradiction between what the US government says and what it does regarding Afghanistan peace talks," the president's spokesman Aimal Faizi said.

He said Karzai also disagreed with the name given to the new Taliban office.

"We oppose the title the 'Islamic Emirate of Afghanistan' because such a thing doesn't exist," BBC quoted Faizi as saying.

Karzai also objected to the Taliban flag flying over the new premises.

The first formal meeting between US and Taliban representatives is expected to take place in Doha Thursday.