Premier Li Keqiang delivers a keynote speech at the opening ceremony of the 10th China-ASEAN Expo in Nanning, the capital of South China's Guangxi Zhuang autonomous region, Sept 3, 2013. [Photo/Xinhua]

NANNING, Guangxi - The China-ASEAN Expo (CAEXPO) marked its 10th anniversary on Tuesday with top officials from its 11 member states sowing the seeds for a better next 10 years for the region, what Chinese premier Li Keqiang called the "diamond decade".

Li said the last decade was a "golden decade" and the organization will build a diamond based on the gold. "The trade volume has increased five-fold during the past decade, and ASEAN has become the third-largest trade partner of China," Li said at the opening ceremony of the expo in Nanning, the capital city of Guangxi Zhuang autonomous region.

Gathered in South China's city bordering Southeast Asia, leaders of China and ASEAN vowed to enhance economic cooperation to build a peaceful and stable region.

China will prioritize ASEAN countries in its foreign diplomacies, and goodwill toward its southeastern neighbors is "a longstanding policy" but not "a temporary expedient," Li said while addressing the ceremony.

For the next 10 years, the Chinese premier urged improving the free trade economic zone and expanding maritime cooperation, including the Trans-Pacific Pact (TPP).

"The issue of South China Sea is not a problem with China-ASEAN relations," Li said. "It will not pose a threat to the main picture."

Leaders from Vietnam, Myanmar, Cambodia, Thailand and Singapore also addressed the ceremony. Thailand's Prime Minister Yingluck Shinawatra said cooperation between Thailand and China is a significant part of Sino-ASEAN ties. "Thailand is the largest participant of the expo, and I am looking forward to a new high in our trade volume in the next year," she said.

At the end of the ceremony, the 11 leaders watered the symbolic seeds for the next decade with special resources combined with water collected from the main rivers of the 11 countries 10 years ago.