Vietnamese Prime Minister Phan Van Khai will visit China and Mongolia from May 20 to 26 to enhance the ties between Vietnam and the two countries.

"The purpose of his trip is to continue consolidating and beefing up the comprehensive cooperation ties between Vietnam and China, and to explore possibilities to further develop the relationship with Mongolia, especially in economy and trade," Le Dung, spokesman of Vietnam's Ministry of Foreign Affairs said on Thursday.

This will be Khai's third visit to China, and his second trip to Mongolia, he added.

Khai is to visit China on May 20-24, and Mongolia on 24-26, at the invitations of Chinese Premier Wen Jiabao and Mongolian Prime Minister Nambaryn Enkhbayar.

The Vietnam-Sino ties, especially economic and trade ones, havedeveloped strongly in recent years. The two-way trade of the two countries stood at 4.6 billion US dollars last year, a year-on-year rise of 42 percent.

By April this year, investors from Chinese mainland and Hong Kong SAR had had 564 projects with a total registered capital of nearly 3.6 billion dollars in Vietnam.