The dispute between China and Vietnam in the South China Sea is complicated and is a problem that is not going to be solved overnight, though the issue shouldn't be overlooked in the bilateral relations, Vietnamese Ambassador to China Nguyen Van Tho said on Wednesday in Beijing.

The South China Sea issue is the only outstanding issue left by history in the relations between Vietnam and China, but the issue is not the overall relationship between the two countries, Nguyen said on Wednesday when giving a speech to students at Beijing Foreign Studies University.

"Of the three historical issues between Vietnam and China, we already solved two,  which were the demarcation of the land border, and the demarcation of the Tonkin Gulf (called Beibu Gulf in China)," said Nguyen.

"This shows that we are capable of solving difficult issues together," the ambassador said.

Nguyen said that both countries agreed to fully and efficiently implement the Declaration on Conduct of Parties in the South China Sea and are working together to build the Code of Conduct in the South China Sea as soon as possible.

Nguyen also noted that both China and Vietnam are at the crossroads of reform and opening up and naturally the relationship with China is one of Vietnam's long-term strategic priorities.

Ma Mingqiang, secretary-general of ASEAN-China Center, said at the same occasion that Chinese leaders attach great importance to relationships with ASEAN countries and view ASEAN as  priority of Chinese foreign policy.

Nguyen called the relationship between Vietnam and China "comprehensive," with political, economic, defense, security, as well as cultural, educational and people-to-people exchanges.

"Leaders of the two countries had decided to build a comprehensive strategic cooperation partnership," said Nguyen, adding that Vietnam President Truong Tan Sang signed the Action Plan to realize the goal during his first state visit to China in June 2013.

In the economic field, China and Vietnam's bilateral trade  has grown from $32 million in 1991 to over $50 billion in 2013, according to the ambassador. But he said Vietnam is also trying to reduce its deficit  with China.