MEXICO CITY, Sept 29 (Reuters) - U.S. and Mexican officials will hold high-level security talks on Oct. 8, Mexico"s Foreign Minister Marcelo Ebrard said on Wednesday. U.S. Secretary of State Antony Blinken, U.S. Homeland Security Secretary Alejandro Mayorkas and U.S. Attorney General Merrick Garland would participate in the talks in Mexico City, Ebrard said. "The main agenda is a document of understanding that we have been working on together with the United States...on the focus and priorities for security," he told reporters at an event in Mexico City.