BRUSSELS (AP) - U.S. Secretary of State John Kerry is joining diplomats from around the world in hopes of persuading Afghan leaders to let international troops remain in the war-torn country beyond 2014. The issue will be among the top priorities at an annual two-day NATO summit in Brussels that begins Tuesday and focuses on security concerns. The U.S. wants to keep thousands of troops in Afghanistan to continue training and advising local forces. Other NATO counties are expected to follow suit once Washington and Kabul reach an agreement. But Afghan President Hamid Karzai so far has balked at the proposal. The U.S. has demanded a final decision by the end of this month, or has threatened to withdraw all its troops from the still shaky country after 12 years of war.