ABC News’ Karen Travers reports: Vice President Biden said today that the coalition forces in Afghanistan have “largely arrested the Taliban momentum” in key areas there. But he acknowledged that the gains are “fragile and reversible.” Biden’s comments came after a meeting with Afghan President Hamid Karzai at the presidential palace in Kabul. Biden emphasized the U.S. commitment to the Afghan government. “We are not leaving if you don't want us to leave,” he said. The vice president said while there are “many hard days that lie ahead,” there is now a “viable path going forward” to the transition from US forces to Afghan security forces by 2014. "We've moved into a new phase in Afghanistan: transition to full Afghan lead beginning this year and concluding in 2014," he said. Biden reiterated the message that a senior administration official conveyed on the trip over – the United States is there to assist the Afghan government, not lead. "It is not our intention to govern or to nation-build,” Biden said. “As President Karzai often points out, this is the responsibility of the Afghan people and they are fully capable of it.” Earlier today Biden visited the Kabul Military Training Center where Afghan National Army troops are trained. A translator explained to the vice president what he was seeing at the training site, including a demonstration of Afghan forces engaged in a training drill in urban terrain. He later greeted each Afghan soldier. Biden received a briefing focused on literacy and leadership training from General Amlaqullah Patiyani, Afghan National Army KMTC Commander, and U.S. Col. Kelly. Vice President Biden’s first stop of the morning was to the US embassy in Kabul and met behind closed doors with about 200 staffers. Biden told the embassy staff that he had spoken to President Obama before the event and the president wanted to convey again how disappointed he was that he was unable to visit the embassy on his trip to Afghanistan in December. Weather precluded Obama from making the helicopter ride from Bagram Air Base to Kabul. Biden emphasized to embassy staff how much he and the president appreciate their hard work and sacrifice. Ambassador Eikenberry gave the Vice President an embassy windbreaker as a souvenir of his trip.