For the first time since the Vietnam War, a US Navy aircraft carrier is paying a visit to a Vietnamese port.
Monday's visit by the USS Carl Vinson, accompanied by a cruiser and a destroyer, seeks to bolster both countries' efforts to stop China's expansion in the South China Sea.
The ships will bring more than 6,000 crew members to the central coastal city of Danang.
It's the largest such US military presence in Vietnam since the Southeast Asian nation was unified under Communist leadership after the war ended in 1975.
The visit comes at a time when China is increasing its military buildup in the Paracel islands and seven artificial islands in the Spratlys in maritime territory also claimed by Vietnam.
"Our hope would be this would restrain China in its various activities in the South China Sea," said Richard Bush, co-founder of the Center for East Asia Policy Studies at the Brookings Institution.
Bush adds it's all about signaling, and backing up your actions.
"For China to push the envelope in this way only drives Vietnam and the Vietnamese people into the arms of the United States," he said.
President Donald Trump called the visit a chance to grow regional security and defense relations between the two countries.
But one political analyst in China claims Vietnam is simply using the US for protection.
"It seems Vietnam does not intend to become an ally of the United States. It is basically a hedging strategy, a kind of balance of power," Joseph Cheng, Hong Kong political scientist and democracy activist, explained.
Cheng says visit irritates China.
"There is some irritation, of course, but Chinese leaders tend to look at the broader picture," he said.
"The leadership is very concerned with the increasing tension between China and the United States as the Donald Trump administration now treats China as a rival and is more concerned with the rise of China and intends to exert further pressure on China both in the security field and also in the economic field," he explained.
China claims most of the South China Sea and has challenged traditional US naval supremacy in the Western Pacific.
The ships' mission is considered a "friendship" visit that includes technical exchanges, sports matches and other community activities, according to a Vietnamese Foreign Ministry spokeswoman.
The US Navy has staged activities in Vietnam for its Pacific Partnership humanitarian and civic missions in nine of the past 12 years.
The United States normalized relations with Vietnam in 1995 and lifted an arms embargo in 2016, and the two former adversaries have steadily improved bilateral relations in all areas, including trade, investment and security.