This will follow the import of the first ever batch of 1 million barrels of WTI crude oil in the first half of this year, Vice Chief Executive Officer Nguyen Van Hoi told Reuters.

Vietnam is seeking to import more goods from the United States to help narrow a favourable trade surplus following threats by U.S. President Donald Trump to impose tariffs on products from the Southeast Asian nation amid a Sino-U.S. trade war.

"Other than WTI crude, we will continue using Vietnam's Bach Ho crude and imported crude oil from other sources in Asia for the refinery," Hoi said by telephone.

Vietnam has been relying more on imported crude due to a slowdown in domestic output as reserves decline at existing fields and China's increasingly assertive stance in the region hampers offshore exploration.

Binh Son will shut down the refinery, which can process 130,000 barrels per day of crude oil, for 51 days starting from early June next year for a major maintenance, Hoi said.

This will be the fourth time the refinery in the central province of Quang Ngai has undergone a major maintenance since it began commercial production 10 years ago.

The refinery operated at 106% of its design capacity in the first half of this year, producing 3.38 million tonnes of refined products, the company said.

Vietnam's trade surplus with the United States widened to $20.59 billion in the first half of this year from $15.55 billion a year earlier, according to Vietnam's official customs data.

Vietnam's Ministry of Industry and Trade and the U.S. Department of Energy will soon sign a memorandum of understanding on LNG imports, the government said in a statement late last month.

(Reporting by Khanh Vu; editing by Christian Schmollinger and Richard Pullin)

By Khanh Vu