Image caption Negotiating with the Taliban is thought to be the best way to end the decade-long conflict

The Taliban say they have reached a preliminary agreement to set up a political office, possibly in Qatar, as part of Western plans to end the war.

A statement confirmed the move, which has been backed by Afghan President Hamid Karzai.

Both the US and Germany have been pushing for such a representation in an effort to kick-start negotiations.

The White House said it welcomed "any step along the road" towards reconciliation.

President Barack Obama "has made clear that we would support and participate in Afghan-led reconciliation efforts", said spokesman Jay Carney.

But he added that reconciliation would only come if the Taliban renounced violence, broke with al-Qaeda and abided by the Afghan constitution.

The move was also welcomed by the Afghan High Peace Council, which is seeking a negotiated end to the war, as "a gesture of good faith".

But it still remains unclear if the insurgents, who claim to be winning the war, are prepared to engage in truly meaningful peace talks - and whether these could take place while international forces continue to kill Taliban fighters and commanders, says the BBC's Quentin Sommerville in Kabul.

Meanwhile at least 12 people including police were killed in three bomb attacks in the southern city of Kandahar, local officials said.

Importance of address

In their statement, the insurgents said Afghanistan's "current problem" began with the US-led invasion of 2001 and "the two main sides which were involved in this are the Islamic Emirate of Afghanistan [Taliban] and on the other side is the United States and their foreign allies".

Analysis The establishment of an office is thought by some to be a critical step in reaching a political settlement to the 10-year long conflict. It would give the group an address where negotiators could meet. Establishing the authenticity of would-be negotiators from the Taliban has been a problem in the past. It is the US and Germany that have been pushing for this. Earlier preconditions that the insurgents would have to lay down arms before any such representation appear to have been dropped. The push for a peace process, with a reluctant President Karzai falling in line, appears to be under way. Some senior military commanders here say that the Bonn conference, where the international community gave a long-term commitment to Afghanistan, was a wake-up call for the insurgents. They face the prospect of growing old, as exiles, in the Pakistani city of Quetta, commented one senior Isaf commander. But it is far from certain that the Taliban truly want to negotiate. They know foreign troops are leaving in 2014. And there will be reluctance from some within the group's leadership to sit down and talk with representatives from countries who are killing Taliban soldiers and commanders.

It said the Taliban movement "always tries to solve the issue or the problem with the opposite side through talks" and warned the Western coalition that they would "never force the Afghans to obey them by force".

"For the sake of a better understanding with the internationals, we have an initial understanding to have a political office - including in the country of Qatar."

The statement added that they wanted prisoners released from the US-run detention centre in Guantanamo Bay, as part of a deal.

Our Kabul correspondent says this could prove difficult, as many Taliban fighters held there have direct links to al-Qaeda and some are responsible for the deaths of Americans.

The statement also rejected as false reports by "Western press and officials" about negotiations.

The agreement to set up the liaison office would give the group an address where negotiators could meet, says our Kabul correspondent, and some see this agreement as a critical step.

But the statement fails to mention the Afghan government, which the Taliban regards as a puppet regime.

String of setbacks

Last month, President Karzai gave his first public support to the plan - having previously rejected the idea, angry that the US and Germany had discussed potential locations without him.

Kabul has repeatedly stressed that it will not accept any foreign intervention in negotiations with the Taliban.

Efforts to hold talks have been hit by a string of setbacks, including the assassination in September of Burhanuddin Rabbani, the head of the peace council, which had been liaising with the militant group.

The Taliban denied being responsible, but said the attack added to the sense of mistrust.

A senior negotiator on the council, Arsala Rahmani, said the Taliban needed to be in touch with the international community.

"We welcome their decision to set up a political office," he told Reuters news agency.

"It is a gesture of good faith. The Taliban are blacklisted by the US so it is very important for them to engage in talks with the US."

US and Afghan officials have also stressed that Pakistan - where the Taliban's leadership are believed to be based - must be involved in the process.