A US Navy aircraft carrier will port in Vietnam in March, a first for the allies and former foes, Defense Secretary Jim Mattis said Thursday. The announcement came as Mattis visited Vietnam following a stopover in Indonesia on a brief Asia tour aimed at drumming up defense cooperation. On his two-day trip to Vietnam, where he met with his counterpart Ngo Xuan Lich and President Tran Dai Quang on Thursday, Mattis zeroed in on freedom of navigation in the resource-rich South China Sea, a thorny issue between Hanoi and Beijing.  China claims most of the waterway -and has built up islands and military installations in the sea. Vietnam, Taiwan, the Philippines, Malaysia and Brunei also have claims in the waterway.  Vietnam and US defense officials have submitted requests for the aircraft carrier to visit, according to Vietnams ministry of defense on Thursday.   Mattis thanked Vietnam for the "increasing partnership with our aircraft carrier coming into Danang in March".  Though smaller US ships have docked on Vietnamese shores, Mattis spokesman Jeff Davis confirmed it will be the first time a US aircraft carrier will port in Vietnam.  US aircraft carriers neared Vietnamese shores during the Vietnam War which ended in 1975, but this will be the first time for a carrier to port in the country, Pentagon officials said. Mattis joined the Marine Corps Reserves in 1969, while the decade-long Vietnam War was ongoing, but did not serve in Vietnam. Next week will mark the 50th anniversary of the Tet Offensive, in January 1968, when the Communist North launched synchronized, simultaneous attacks on multiple targets in US-backed South Vietnam, including the city of Hue. The offensive was a military failure, but it turned out to be a pivotal point in the war by puncturing US hopes of a swift victory. The war dragged on for another seven years before the US completed its withdrawal.