The United States on Thursday partially lifted a long-time ban on lethal weapon sales to Vietnam to help it improve maritime security, a historic move that comes nearly 40 years after the American war in Vietnam.

"The State Department has taken steps to allow for the future transfer of maritime security-related defense articles to Vietnam," State Department spokeswoman Jen Psaki told a briefing.

State Department officials told a separate briefing that the decision would ease a ban on sales of lethal weapons to Vietnam that has been in place since the end of the American war in Vietnam, although only for maritime security purposes at this point.

They said requests from Vietnam for any specific weapons would be evaluated on a case-by-case basis.

The focus would be on helping Vietnam patrol and defend itself in the East Vietnam Sea, amid growing naval challenges from China, the officials said, but future weapons sales could include airborne systems as well as ships.

U.S. Senator John McCain, a former prisoner of war in Vietnam, welcomed the news.

"Easing the lethal arms ban on Vietnam for the purpose of maritime security will strengthen our defense cooperation in ways that benefit both countries," McCain said.

Vietnam's foreign minister last week said his country would welcome an end to the arms embargo after Reuters reported that Washington was nearing such a decision.

U.S. sources have said Washington could eventually sell Vietnam used U.S. P-3 Orion surveillance planes built by Lockheed Martin Corp, which are being replaced by newer P-8A aircraft built by Boeing Co.

The State Department officials declined to name any specific weapons systems that could be under consideration or give a timetable for expected agreement on the first such deal. They said providing surplus U.S. defense equipment to Vietnam could trim the cost, but Vietnam would need to contribute as well.

"This is a very important first step that will engender future cooperation," said one of the officials. "This policy revision enables us to ... provide Vietnam the ability to defend itself in the context of its presence” in the East Vietnam Sea.

The officials said they did not expect backlash from China since the focus would be on providing Vietnam with defensive systems. "This is not an anti-China move," said one of the officials.

The easing of the embargo follows a gradual resumption of links between the United States and Vietnam over two decades.

U.S. industry executives see Vietnam as a promising market for their equipment given the U.S. military's strategic rebalance to the Asia-Pacific region.