KABUL – US Vice President Joe Biden stressed Tuesday that his country's troops could stay in Afghanistan after 2014 if Afghans want them to, on day two of a surprise visit to the war-torn nation.
Speaking after talks with President Hamid Karzai in Kabul, Biden said: "We're not leaving if you (Afghans) don't want us to leave".
But he also emphasised that the planned handover of responsibility for security from international troops to Afghan forces in four years, agreed at a NATO summit in November, was on track.
"It's not our intention to govern or to nation-build -- as President Karzai often points out, this is the responsibility of the Afghan people," Biden told reporters at a press conference.
"We stand ready to help you in that effort and we'll continue to stand ready to help you in that effort after 2014."
A senior White House official said Biden was not announcing a change in policy.
"The vice president was simply restating for the public what he had said to the president (Karzai) which was that the United States wants an enduring partnership with Afghanistan," the official said.
There are about 97,000 United States troops serving in Afghanistan as part of an international force of some 140,000.
Limited, conditions-based withdrawals are due to start in July ahead of the scheduled 2014 transition.
In 2010, coalition troops suffered their bloodiest year yet in Afghanistan with 711 deaths, according to the icasualties.org website, while opinion polls suggest increasing numbers of Americans want their troops to come home.
Biden said Afghanistan was now in a "new phase" and insisted that Taliban momentum had been "largely arrested" in key areas such as the southern provinces of Helmand and Kandahar.
His comments came despite several recent attacks in the south, seen as the focus of the war, including a suicide bombing at a bath house in Kandahar province last week which killed 17 people.
"We have a strategy and the resources in place to accomplish the goal of a stable and a growing and an independent Afghanistan able to provide for its own security," Biden said.
But he added that gains made were "fragile and reversible and the president knows that sustaining them is going to require the Afghans to improve... security and governance".
Karzai said he and Biden had held one-to-one talks that lasted one hour and 45 minutes.
"We discussed the transition process in 2014 and how best to proceed with it. We had a good discussion, it made me happy," Karzai told the press conference, which came a day after Biden's surprise arrival in Afghanistan.
Biden held talks and had lunch with Karzai after visiting a training facility for Afghan security forces just outside Kabul. He later met US troops serving in Wardak province, central Afghanistan, plus local officials.
Shortly after arriving late Monday, Biden spent nearly two hours with the commander of international troops in Afghanistan, US General David Petraeus, and US ambassador Karl Eikenberry.
A US official travelling with Biden said the vice president's trip came at a "pivot point" for the US in Afghanistan, adding it would allow Biden to review progress towards handing responsibility for security to Afghan forces.
The complex relations between the Western-backed government in Kabul and the US were laid bare by recent comments by Karzai accusing foreign countries of meddling in Afghanistan.
And last month, whistleblowing website WikiLeaks published leaked cables in which Eikenberry described Karzai as sometimes "paranoid and weak".
The ambassador also reportedly highlighted corruption among key government officials in Afghanistan.
The visit, Biden's first to Afghanistan since taking office, was not pre-announced due to security concerns, although Karzai was informed of the trip last week, the US official told reporters.
Biden's trip began four days after the US announced it was sending an extra 1,400 Marines to southern Afghanistan, seen as the heart of the Taliban insurgency, in a bid to pre-empt an expected spring offensive in April or May.