China’s Vice Premier Zhang Gaoli delivers a speech on “China’s Economy in the New Normal” at the opening ceremony of China Development Forum, in Beijing March 22, 2015. REUTERS/Jason Lee

Chinese Vice Premier Zhang Gaoli, a member of the ruling communist party’s elite Politburo Standing Committee, will visit Vietnam in mid-July, state media said on Monday, amid tension over territorial disputes in the Eastern Sea. China’s official Xinhua news agency did not give dates for the trip, but Vietnam’s Foreign Ministry said on its website the visit would be between Thursday and Saturday. Zhang was invited by Vietnam’s ruling communist party, but no details were given of the purpose of the visit. China’s increasingly assertive moves to press sovereignty claims in regional waters have rattled its neighbours and aroused concern in the United States, although Beijing says it has no hostile intent.

China has overlapping claims with Vietnam, the Philippines, Malaysia, Taiwan and Brunei in the South China Sea, through which $5 trillion in ship-borne trade passes every year. Washington has taken advantage of the row to ramp up diplomacy with Hanoi after China parked an oil rig unannounced in waters that Vietnam considers its domain. China’s deployment of the rig last year, in what Vietnam called its exclusive economic zone and on its continental shelf, about 120 nautical miles off its coast, led to the worst breakdown in relations since a brief border war in 1979.