The Afghan Taliban said on Tuesday they have reached a preliminary agreement to set up a political office in the Gulf nation of Qatar, and asked for the release of prisoners held at the U.S. military prison at Guantanamo Bay.

The Taliban office is seen by Western and Afghan officials as a crucial step to moving forward with secretive attempts to reach a negotiated end to a decade of war in Afghanistan

It was welcomed by one of the Afghan government's top peace negotiators as a gesture of good faith, from a group which in the past has laid down strict pre-conditions for any talks including the withdrawal of all foreign forces.

We are right now ready ... to have a political office overseas, in order to have an understanding with the international (community), spokesman Zabihullah Mujahid said in an emailed statement.

In this regard we have reached an initial understanding with Qatar and relevant sites.

The Afghan government had pushed for an office in Saudi Arabia or Qatar, but said in late December that Kabul would accept a Taliban liaison office in Qatar, if its officials retained control of the negotiating process.

A senior member of Afghanistan's High Peace Council, the body charged with seeking a negotiated end to the country's decade-long war, said he welcomed the Taliban's decision to set up a political office in Qatar.

It is important for the Taliban to negotiate with the international community, especially with the U.S, and we welcome their decision to set up a political office, Arsala Rahmani, a top negotiator on the high peace council, told Reuters.

It is a gesture of good faith.

Senior U.S. officials told Reuters last month that, after 10 months, talks with the Taliban had reached a critical juncture, and as part of the accelerating, high-stakes diplomacy, the United States is considering the transfer of several high-profile Taliban prisoners from Guantanamo into Afghan custody.

The move came as a suicide bomber killed four children and a policeman and wounded 16 others, including six children, in the southern city of Kandahar on Tuesday, said Zalmai Ayobi, the provincial governor's spokesman.

KABUL IGNORED?

The call for a permanent international address for the Taliban came after a series of failed efforts towards talks by Afghans and their Western allies, some of them with interlocutors who turned out to be frauds.

These culminated in the September 2011 killing of Karzai's top peace envoy, former Afghan President Burhanuddin Rabbani, by a man accepted as a Taliban representative, which appeared to temporarily destroy the president's appetite for negotiations.

An office in Qatar would also help address Afghan worries about the influence of the Pakistani government over the insurgent group, whose leaders are mostly believed to be based across the border from their homeland.

But Afghan leaders have expressed concerns that any office be used only as an address to help negotiators verify the identity of anyone claiming to represent the Taliban, rather than as a base to build political clout.

They are also concerned about being marginalised in a process they do not control.

Karzai declined immediate response to the statement, but may be concerned by its emphasis only on communication with the international community -- there is no reference to the current Afghan government.

Both the president's team and U.S. officials working on negotiations have repeatedly insisted that they be Afghan-led but the Taliban statement explicitly casts their war as a battle only with foreigners.

The two main sides which were involved in this are the Islamic Emirate of Afghanistan and on the other side is the United States and their foreign allies, Mujahid said, using the Afghan Taliban's own name for its movement.

The Taliban statement also dismissed as untrue reports about talks that appeared in the Western press, and specified that the office aimed to improve ties -- suggesting any further progress might be slow.

(Reporting by Hamid Shalizi; Writing by Emma Graham-Harrison; Editing by Ed Lane)