China and Vietnam plan to hold their first joint army training exercise this month, a sign of deepening military ties as the two countries grapple with U.S. tariff policies.

The exercise aims to strengthen practical cooperation between the two militaries, the Chinese defense ministry said in a Sunday statement. It will take place in southern China’s Guangxi region, which borders Vietnam.

China and Vietnam have carried out joint naval patrols in previous years, but the coming exercise would be the first such exchange between their armies.

Vietnam, an export powerhouse that last year had the world’s third-biggest trade surplus with the U.S., is seeking to persuade Washington to lower tariffs on Vietnamese goods. The Southeast Asian nation was caught off guard by U.S. President Donald Trump’s announcement earlier in July that they had agreed to a 20% tariff, it was reported.

Vietnam is also striving to balance relations with its largest trading partner, China, which has warned nations against cutting deals at Beijing’s expense. After Trump announced the pact with Vietnam in July, China’s commerce ministry said it was "assessing” the situation. Chinese President Xi Jinping called for joint efforts with Vietnam to oppose "unilateral bullying” during his visit to the country in April.