KABUL, Afghanistan (AP) — Secretary of State John Kerry sought Friday to broker a deal between Afghanistan's rival presidential candidates as a bitter dispute over last month's runoff election risked spiraling out of control. Kerry, who arrived predawn in Kabul on a hastily arranged visit, is meeting with former Finance Minister Ashraf Ghani Ahmadzai and former Foreign Minister Abdullah Abdullah as well as the current leader, President Hamid Karzai. The objective is to convince both candidates to hold off on declaring victory or trying to set up a government until the United Nations can conduct an audit of extensive fraud allegations in the voting. For the United States, the political crisis is threatening to undermine more than a decade of efforts to leave behind a strong Afghanistan capable of containing the Taliban insurgency and preventing extremist groups like al-Qaida from using the territory to endanger the American homeland. "We are in a very, very critical moment for Afghanistan," Kerry told reporters after meeting the U.N.