BEIJING (Reuters) - China’s defense ministry said on Thursday that navy chief Shen Jinlong plans to visit the United States in September, despite an escalating trade row that threatens to spill into other areas of tension between the two countries.

FILE PHOTO: China's aircraft carrier Liaoning takes part in a military drill of Chinese People's Liberation Army (PLA) Navy in the western Pacific Ocean, April 18, 2018. Picture taken April 18, 2018. REUTERS/Stringer

The announcement the ministry’s spokesman Wu Qian comes two months after U.S. Defense Secretary Jim Mattis visited Beijing. China said that visit yielded positive results, and Defense Minister Wei Fenghe has accepted an invitation to visit the United States before the end of the year.

Speaking at a regular monthly news briefing, Wu said that Shen plans to visit the United States in the middle or towards the end of next month, to attend an international naval forum and also to pay a working visit to the country.

He gave no other details.

Ties between the two countries have been strained on a number fronts in recent months.

In May, the Pentagon withdrew an invitation to China to join a multinational naval exercise, citing China’s military moves in the South China Sea. The U.S. decision upset Beijing and was raised during the visit by Mattis, Chinese officials said at the time.

Beijing and Washington are also locked in a spiraling trade row that is threatening to worsen the relationship across the board, from cooperation on North Korea to the disputed South China Sea.

U.S. backing for self-ruled Taiwan have also fueled China’s suspicions in recent months, as the current U.S. administration has signaled fresh support towards the island that Beijing claims as its own.

The navy has been a key part of President Xi Jinping’s ambitious military modernization program that has rattled nerves around the region, though China says it has no hostile intent.

Wu separately announced that the country’s second aircraft carrier has begun its second round of sea tests, leaving from its base in the northern port city of Dalian, where it was built.

China’s Maritime Safety administration earlier on Thursday said an area of the northern part of the Yellow Sea off Dalian would be closed to shipping for military drills from Friday for a week-long period.

The still-unnamed carrier, the first to be built domestically, was launched last year, but Chinese military experts have told state media it is not expected to enter service until 2020, once it has been fully kitted out and armed.

Little is known about China’s aircraft carrier program, which is a state secret. But the government has said the new carrier’s design draws on experiences from the country’s first carrier, the Liaoning, which was bought second-hand from Ukraine in 1998 and refitted in China.