US President Barack Obama has fully lifted the ban on the sale of lethal weapons to Vietnam.
The move aims to enhance defence cooperation between the two countries.
The New York Times quotes Obama as saying: "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 toward normalisation with Vietnam."
The countries have committed to jointly resolve territorial and maritime security issues, including recent developments in the South China Sea.
Both the countries called for non-militarisation and self-restraint in addressing disputes under the Sunnylands Declaration.
The US and Vietnam will also focus on humanitarian cooperation, peacekeeping, and humanitarian assistance and disaster relief.
They will also work to combat transnational crime and cyber-security attacks.
The US is providing maritime security assistance to Vietnam through the Maritime Security Initiative (MSI), the Cooperative Threat Reduction programme, and foreign military financing.
Hanoi received defensive maritime equipment shipments from the US in October 2014.