The president said it was part of a move towards "normalizing" relations between the two countries.

The U.S. will allow the sale of deadly weapons to Vietnam for the first time since the war between the two countries ended in 1975, President Obama announced during a visit to the east Asian country on Monday.

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The president, speaking at a news conference with his Vietnamese counterpart Tran Dai Quang, said the decision would remove the "lingering vestige of the Cold War".

"At this stage both sides have developed a level of trust and cooperation," Obama said.

The president, speaking during a three-day visit visit to the communist country ahead of his trip to Japan, is attempting to shore-up relations with Asia-Pacific nations.

The U.S. is walking a diplomatic tightrope regarding disputed waters – among the busiest shipping passages in the world – in the South China Sea.

The Chinese government has been making aggressive moves towards claiming islands and territories that other nations say belong either to them, or are in international waters. Vietnam has pushed back against China's efforts.

Speaking to reporters in Hanoi, President Obama said the lifting of sanctions was unrelated to policy on China, but instead part of a "lengthy process of moving towards normalization" with Vietnam.