KABUL — Former Foreign Minister Abdullah Abdullah's lead slightly increased in partial results for Afghanistan's presidential election released Sunday, but he and rival Ashraf Ghani Ahmadzai still seem to be heading for a runoff next month. The winner will replace Hamid Karzai, the only president the country has known since the 2001 US-led invasion ousted the Taliban, and will oversee a tumultuous period as the US and NATO are expected to withdraw most of their troops from the country by the end of this year. Karzai, whose relations with Washington have sharply deteriorated, was constitutionally barred from running for a third term. The latest numbers showed Abdullah with 44 percent of the vote tallied so far. Ahmadzai, a former finance minister and World Bank official, received 33.2 percent in the partial results. Zalmai Rassoul, another ex-foreign minister, had 10.4 percent. Final results aren't due until May 14. Both Abdullah and Ahmadzai have promised a fresh start with the West and have vowed to move ahead a security pact with the US that Karzai has refused to sign. That pact would allow a small force of American soldiers to stay in the country to continue training Afghan army and police to fight the Taliban. The results announced by Ahmad Yousuf Nouristani, the chairman of Afghanistan's Independent Election Commission, represent about half of the estimated 7 million ballots cast in the April 5 poll. — AP