In a move calculated to respond to China's military build-up in the region, President Obama announced that the U.S. is lifting its decades-old ban on the sale of lethal arms to Vietnam.

The lifting of the embargo will be seen by China as an escalation of tensions in the region, although Washington denies that the move is aimed at Beijing.

The president is in Vietnam ahead of the G-7 Summit in Japan.

Reuters:

The move came during President Barack Obama's first visit to Hanoi, which his welcoming hosts described as the arrival of a warm spring and a new chapter in relations between two countries that were at war four decades ago.

Obama, the third U.S. president to visit Vietnam since diplomatic relations were restored in 1995, has made a strategic 'rebalance' toward Asia a centerpiece of his foreign policy.

Vietnam, a neighbor of China, is a key part of that strategy amid worries about Beijing's assertiveness and sovereignty claims in the South China Sea.

The decision to lift the arms trade ban, which followed intense debate within the Obama administration, suggested that such concerns outweighed arguments that Vietnam had not done enough to improve its human rights record and that Washington would lose leverage for reforms.

Obama told a joint news conference with Vietnamese President Tran Dai Quang that disputes in the South China Sea should be resolved peacefully and not by whoever "throws their weight around". But he insisted the arms embargo move was not linked to China.

"The decision to lift the ban was not based on China or any other considerations. It was based on our desire to complete what has been a lengthy process of moving towards normalization with Vietnam," he said. He later added that his visit to a former foe showed "hearts can change and peace is possible".

The sale of arms, Obama said, would depend on Vietnam's human rights commitments, which would be made on a case-by-case basis.

Expect more of these bilateral security arrangements with other countries in the region, including the Philippines, whose fishing fleet has been contininously harassed by the Chinese navy.  China's provocative actions in building an island and militarizing it have alarmed the administration, and China's aggressive posture has sent tensions in the region skyrocketing.

War in the South China Sea?  China may feel forced to respond to the U.S. lifting the Vietnam arms embargo.  This sort of tit-for-tat diplomacy has been known to get out of hand, with war being an unintended outcome.  But none of the nations involved – including the U.S. and China – wants war, so the hope that cooler heads will prevail seems reasonable.