WASHINGTON, June 25 (Reuters) - U.S. President Joe Biden met Afghan President Ashraf Ghani and his former political foe, Abdullah Abdullah, on Friday to discuss Washington"s support for Afghanistan as the last U.S. troops pack up after 20 years of war and government forces struggle to repel Taliban advances. Biden, seated beside Ghani and Abdullah in the Oval Office, called them "two old friends" and said U.S. support for Afghanistan was not ending but would be sustained despite the U.S. pullout. “Afghans are going to have to decide their future, what they want," said Biden, saying the “senseless violence has to stop.” Ghani said Afghan security forces had retaken six districts on Friday. He said he respected Biden"s decision and that the partnership between the United States and Afghanistan is entering a new phase. “We are determined to have unity, coherence," he said. The Oval Office meeting could be as valuable to Ghani for its symbolism as for any new U.S. help because it will be seen as affirming Biden"s support for the beleaguered Afghan leader as he confronts Taliban gains, bombings and assassinations, a surge in COVID-19 cases and political infighting in Kabul. "At a time when morale is incredibly shaky and things are going downhill, anything one can do to help shore up morale and shore up the government is worth doing," said Ronald Neumann, a former U.S. ambassador to Kabul. "Inviting Ghani here is a pretty strong sign that we"re backing him." Biden"s embrace, however, comes only months after U.S. officials were pressuring Ghani to step aside for a transitional government under a draft political accord that they floated in a failed gambit to break a stalemate in peace talks. Hours before the talks, Biden said on Twitter that he looked forward to the meeting and that "as the U.S. military drawdown continues, we affirm our enduring support for the Afghan people." He has asked Congress to approve $3.3 billion in security assistance for Afghanistan next year and is sending 3 million doses of vaccines there to help it battle COVID-19. Biden will urge Ghani and Abdullah, foes in Afghanistan"s two last presidential elections, "to be a united front" and he will reaffirm U.S. support for a negotiated peace deal, said White House deputy press secretary Karine Jean-Pierre. U.S. officials, however, have been clear that Biden will not halt the American pullout – likely to be completed by late July or early August – and he is unlikely to approve any U.S. military support to Kabul to halt the Taliban"s advances beyond advice, intelligence, and aircraft maintenance. Before heading to meet Biden, Ghani and Abdullah, chairman of Afghanistan"s High Council for National Reconciliation, met at the Pentagon with U.S. Defense Secretary Lloyd Austin and other top U.S. civilian and military officials. Austin reaffirmed continued U.S. security aid to Afghanistan, according to a pool report from the opening of the talks. Speaking of a "new phase" in the U.S.-Afghan relationship, Ghani asserted that the "narrative of abandonment is just false," and that his forces have made "significant progress" even though the situation "presents challenges," the pool report said. Earlier, the Afghan leaders met for a second day on Capitol Hill, where Biden"s withdrawal decision met objections from many members of both parties. U.S. House of Representatives Speaker Nancy Pelosi, welcoming Ghani to a bipartisan leadership meeting, said she looked forward to hearing about what more can be done with U.S. humanitarian aid, especially for women and girls. Many lawmakers and experts have expressed deep concerns that the Taliban - if returned to power - will reverse progress made on the rights of women and girls, who were harshly repressed and barred from education and work during the insurgents" 1996-2001 rule. WORRIES ABOUT AL QAEDA The Ghani-Abdullah visit comes with the peace process stalled and violence raging as Afghan security forces fight to stem a Taliban spring offensive that threatens several provincial capitals and has triggered mobilizations of ethnic militias to reinforce government troops. U.S. Secretary of State Antony Blinken, speaking during a visit on Friday to Paris, said Washington is "looking very hard" at whether the Taliban are "serious about a peaceful resolution to the conflict." read more The crisis has fueled grave concerns that the Taliban could regain power - two decades after the U.S.-led invasion ended their harsh version of Islamist rule – allowing a resurgence of al Qaeda. U.S. and U.N. officials say the extremists maintain close links with the Taliban. U.S. officials respond that the United States will be able to detect and thwart any new threats by al Qaeda or other Islamists. The Taliban insist al Qaeda is no longer in Afghanistan. U.S. government sources familiar with U.S. intelligence reporting describe the situation as dire. Ghani, they said, has been urged to do more to step up pressure on the insurgents while U.S.-led coalition forces are still there. Reporting by Jonathan Landay and Steve Holland; Additional reporting by Patricia Zengerle, Phil Stewart, Idrees Ali and Mark Hosenball; Editing by Mary Milliken and Daniel Wallis