US Secretary of State John Kerry talks to students who gathered to see him before a speech in Tan An Tay along the Mekong River Delta on Sunday. It was the first time Kerry has returned to the Mekong River Delta since he commanded a swift patrol boat during the Vietnam War.[Agencies]

US Secretary of State John Kerry offered assistance to protect Vietnam's disputed maritime borders with China in the South China Sea in exchange for more trade and security cooperation during a visit to the country on Monday.

On his first trip to Vietnam as the United States' top diplomat, Kerry was in the capital, Hanoi, on Monday seeking to assure the Vietnamese of the US commitment to freedom of navigation and the peaceful resolution of disputes, amid tensions with China over conflicting territorial claims in the South China Sea.

"Cooperation in the region should never be black or white. There is plenty of potential for all parties to seek common interests," said Qi Jianguo, China's former ambassador to Vietnam.

Relations between Vietnam and the US have been warming recently, especially after the two countries established a comprehensive partnership when Vietnamese President Truong Tan Sang visited the US this summer. Qi said a good relationship with Vietnam is important for the US' rebalancing strategy in the Asia-Pacific region.

"Vietnam is not an ally for the US yet, but the country has a significant strategic location in the region. Besides enhancing ties with its traditional partners in Southeast Asia, the US also needs to find new support to strengthen its rebalancing strategy," Qi added.

The US is currently negotiating a major trade agreement with 11 Asia-Pacific nations, including Vietnam.

Chu Hao, a research scholar at the Institute of South and Southeast Asian and Oceania Studies of the China Institutes of Contemporary International Relations, said the US is using trade promotion, maritime security assistance and energy cooperation with Vietnam as a way to press the Southeast Asian country on reforms.

"Even though Vietnam works efficiently to meet the US' ideas in bilateral cooperation, Hanoi is very clear about Washington's attempts," he said.

There are still many uncertainties in the relationship between the two countries, Chu added.

However, the intention of the cooperation recently promoted in the region by the US and Japan is quite obvious, he said, referring to the summit between Japan and ASEAN.

"They aim to push ASEAN to the opposite side of China. Those actions damaged relations between China and the region," Chu added.

Even though China is Vietnam's largest trading partner, the increase in trade between Vietnam and the US should still deserve more attention from China, he added.

"Vietnam is an export-oriented economy, which relies on the trade surplus to boost domestic growth. But Vietnam has a significant trade deficit with China, which is even bigger than the surplus they made from the US, their second-largest trading partner," Chu said.

AP contributed to this story.