The United States and the Taliban cleared the decks for peace talks Tuesday even as a deadly attack on US troops underlined the still furious nature of their decade-long war.

US officials welcomed the Islamist insurgent group's opening of an office in Qatar to serve as a front for talks with Washington and President Hamid Karzai's Afghan administration, and said the sides would meet this week.

But the dramatic announcements were marred just hours later by yet more violence, with four American soldiers killed by insurgent fire at the sprawling Bagram air base, north of Kabul, military officers said.

It also coincided with NATO's formal transfer of responsibility for Afghan security to Karzai's forces. The US-led international combat mission is due to wind down next year, with Afghanistan still in the grip of fighting.

The Taliban had broken off contact with the Americans last year and has refused to negotiate with Kabul, but spokesman Zabiullah Mujahid told AFP the office was intended "to open dialogue between the Taliban and the world."

US President Barack Obama called the planned talks an "important first step" but warned of a long and bumpy road ahead.

"An Afghan-led and Afghan-owned peace process is the best way to end the violence and to ensure lasting stability in Afghanistan and the region," Obama said on the sidelines of the G8 summit in Northern Ireland.

Obama insisted the Taliban would have to renounce ties to Al-Qaeda, halt violence and commit to the protection of women and minorities, and warned that US-led NATO forces remain "fully committed" to battling Al-Qaeda.

The Taliban, which was driven from power in the wake of the September 11, 2001 attacks by US-backed rebels, has since mounted a guerrilla war against the Afghan government and maintains rear bases in Pakistan.

Pakistan, which has battled its own Islamist insurgency but is widely seen as quietly backing the Afghan Taliban, said it welcomed the peace talks.

UN Secretary General Ban Ki-moon also welcomed the talks, with a spokesman saying dialogue is "the only way to end the violence."

With the war at a stalemate, a huge US-led NATO army is concentrating on training Afghan government troops to take charge when most international forces leave in the course of next year.

In parallel, US envoys are attempting to open a dialogue with the main Taliban faction, in the hope of convincing it to repudiate its ties with Al-Qaeda and to reach a political deal with Karzai.

A US official said American and Taliban envoys would meet in Doha "in a couple of days," after which the Taliban would meet with a "High Peace Council" set up by Karzai to conduct the negotiations.

In opening its mission, the Taliban did not explicitly renounce Al-Qaeda, which prior to 9/11 and the US intervention had bases in Afghanistan, but it did vow not to allow attacks to be launched from Afghan soil.

This proved a sufficient first step for US officials, and State Department spokeswoman Jen Psaki said that an eventual disavowal of Al-Qaeda ties by the Taliban was only an "end goal of the process."

Psaki could not say when the meeting would take place, but said Ambassador James Dobbins, US special representative for Afghanistan and Pakistan, would leave Washington later Tuesday bound for Doha to lead the US teams.

The divided Afghan insurgency could complicate talks, amid US doubts as to whether the powerful "Haqqani network" of warlord Jalaluddin Haqqani, a former CIA asset turned Al-Qaeda ally, was ready to embrace negotiation.

US officials said the Taliban envoys in Doha had been authorized to talk by Mullah Omar, the main Taliban figurehead, and that Haqqani's group is "a fully subordinate part of the overall insurgency."

But General Joseph Dunford, the US commander in Afghanistan, said he was skeptical the Haqqanis would back a peace deal.

Officials said this week's ground-breaking meeting would amount to "an exchange of agendas," followed by another within about two weeks.

The Taliban said it supports a "political and peaceful solution that ends Afghanistan's occupation and guarantees the Islamic system and nationwide security."

Karzai, who has long called for peace talks, said he had ordered government envoys to travel to Qatar to try to open negotiations.

He pledged that Afghan forces were ready to take on the insurgents, but the enduring threat was underlined when a bomb targeting a lawmaker killed three people just before the security handover ceremony Karzai attended.

The turnover of the last districts from NATO to Afghan control included areas in the south and east where the Taliban are at their strongest.

Doubts remain over the ability of Afghan forces to maintain security, and the 98,000 foreign troops still in Afghanistan will retain an important function in training, logistics, air support and in combat emergencies.

Britain's Cameron backs US-Taliban talks
Enniskillen, United Kingdom (AFP) June 18, 2013 - British Prime Minister David Cameron said the United States was doing the right thing by meeting with Taliban representatives after the Afghan militants opened an office in Qatar.

Speaking at the end of the G8 summit in Northern Ireland, Cameron said leaders had discussed the issue during a dinner on Monday night during which they focused on foreign policy.

"I think this is the right thing to do, of course it involves all sorts of difficulties," Cameron told a news conference at the summit on the edge of a lake in the luxury Lough Erne golf resort.

Cameron said the security response in Afghanistan, where Britain still has around 7,900 troops and is in the process of handing over to Afghan security forces, had to be matched by a "political process."

"That is exactly what I hope can happen with elements of the Taliban -- that is the point of the Taliban office in Doha in Qatar and that is the point of the discussions that the Americans will have," Cameron said.

"And we've been fully engaged and involved in this process right from the start, indeed from the moment I became prime minister."

Washington announced the talks "in a couple of days" in Doha as the Taliban said they had opened an office there to oversee peace talks.

Cameron highlighted the similarities between the situation in Afghanistan and Northern Ireland, where a 1998 peace accord largely ended decades of Protestant-Catholic violence.

"In the end we're standing in a place where people who were once committed to violence decided to give up that violence and join a political process and that is what is required in Afghanistan," he said.

"That shouldn't signal any weakening of our security response, it absolutely doesn't, but if we can persuade people there is a legitimate political path for them to follow we should do so."

Pakistan welcomes opening of Taliban office
Islamabad (AFP) June 18, 2013 - Pakistan on Tuesday welcomed the Taliban's decision to open an office in Qatar and the subsequent announcement by the US that it will launch talks with the insurgents this week.

The Islamic militia opened a political office in the Qatari capital of Doha with the aim of opening dialogue with the international community and Afghan groups.

The United States immediately welcomed the decision and senior officials said they hoped to meet the Taliban shortly, despite the raft of differences between the two sides.

"Pakistan welcomes the announcement of the opening of a Taliban office in Doha for the purpose of bringing peace to Afghanistan and the region," Pakistani foreign ministry spokesman Aizaz Ahmad Chaudhry said in a statement.

"Pakistan also welcomes the start of direct peace talks between the US and the Taliban."

The Taliban, which has been fighting against US-led NATO troops and the Afghan government for 12 years, broke off contact with the Americans last year and has refused to negotiate with Kabul.

On Tuesday Taliban spokesman Zabiullah Mujahid told AFP the office was intended "to open dialogue between the Taliban and the world".

Chaudhry said Pakistan has long called for an early end to the Afghan war in order to reach a peaceful solution.

"Pakistan is ready to continue to facilitate the process to achieve lasting peace in Afghanistan in accordance with the wishes of the Afghan people," he said.

Senior US officials announced they will begin talks with the Taliban this week.

"I think the US will have its first formal meeting with the Taliban, and the first meeting with the Taliban for several years, in a couple of days in Doha," a US official told reporters, speaking on condition of anonymity.