FILE - In this Sept. 20, 2013 file photo, a US Marine, left, from the 13th Marine Expeditionary Unit BOXER Amphibious Ready Group based in Okinawa, Japan, is greeted by Filipino Marines after jumping from a U.S. helicopter during a joint military exercise called Philippines-U.S. Amphibious Landing Exercise (PHIBLEX) in Ternate, Cavite province, southern Philippines. A new defense pact that will allow thousands of U.S. troops to be temporarily based in Philippines for the first time in more than 20 years signals closer cooperation in the allies’ hot-and-cold relationship that has been shaped over the decades by war, terrorism and now, jitters over China's rise. The 10-year agreement, signed Monday, April 28, 2014, as President Barack Obama arrived in Manila, was considered the centerpiece of his four-nation Asian trip, which he used to reassure allies like Japan and the Philippines of American military backing as they wrangle with China in increasingly tense territorial disputes. (AP Photo/Aaron Favila, File)