Four extra sites opened to search for US troops missing in Vietnam    A file photo of a joint repatriation ceremony at Danang International Airport in June 2012, after Vietnam handed over remains believed to be of American soldiers who died during the war in the 1960s and 70s. Vietnam advised the United States at the start of high-level talks this week it would open four additional sites to investigators seeking the remains of American military personnel missing since the Vietnam War, a senior U.S. defense official said. Deputy Assistant Defense Secretary Vikram Singh, who oversees U.S. military ties with South and Southeast Asia, said an eight-member delegation led by Senior Lieutenant General Nguyen Chi Vinh told U.S. defense officials about the decision at the outset of talks at the Pentagon this week. "They basically opened the meeting by turning over the information and providing us access to an additional four sites for remains recovery operations to go look for our fallen," Singh said, calling it a "really meaningful" gesture.  A U.S. official said on Friday the sites were in the southern part of Vietnam and were small areas where specific incidents are believed to have taken place. Officials declined to elaborate, citing concerns for the families of the missing. The Defense Department's POW/Missing Personnel Office says 1,275 Americans are still unaccounted for from the Vietnam War. The office has investigated 600 of those cases and believes it will not be possible to recover the remains, leaving 675 still being sought. Vinh's delegation visited the Pentagon for talks that take place annually between the former enemies, which have been deepening military ties over the past decade. The pace of contact between the two countries has increased in recent years as the United States has moved to refocus its energies on the Asia-Pacific region after more than a decade of war in Iraq and Afghanistan. The rebalancing takes place amid concerns among Washington and Asian allies about China's growing assertiveness in the region. 'DEEPENING TIES' Then-U.S. Defense Secretary Leon Panetta visited Vietnam last year, stopping at Cam Ranh Bay to visit a U.S. Navy supply vessel undergoing repairs, before traveling to Hanoi for talks with senior defense leaders. "In the year since then, what we've seen is just an across-the-board deepening of defense ties," Singh said in an interview this week. He noted that Secretary of State John Kerry and Defense Secretary Chuck Hagel both served in the Vietnam War and had a special interest in the country. The United States and Vietnam have been cooperating in five areas since signing a memo of understanding in 2011: peacekeeping, maritime security, humanitarian assistance and disaster response, search and rescue, and high-level exchanges. Singh said the two countries had been increasing cooperation on peacekeeping over the past year after Vietnam changed its laws and regulations to permit its military forces to participate in international peacekeeping operations. "We see it as in our interest for all the Southeast Asian nations to be active supporters and contributors to peacekeeping operations," he said. The two sides also set the stage for further cooperation on maritime security during the visit, Singh said. Admiral Robert Papp, commandant of the Coast Guard, and Major General Nguyen Quang Dam, commander of Vietnam's coast guard, signed an agreement formalizing their decision to work together on equipment, training and capacity building. "Having this cooperation is an opportunity for us to work together with them on things that we think will help contribute to overall peace and stability in the South China Sea," Singh said. Reuters