China sent a senior official to Vietnam to enhance “political trust” between the two countries, ahead of a scheduled visit by U.S. President Joe Biden designed to boost diplomatic ties between Washington and Hanoi.

The Chinese Communist Party’s international department head Liu Jianchao met with Vietnam’s ruling Communist Party leader Nguyen Phu Trong, the official Chinese Xinhua news agency reported.

During his three-day trip, which ends on Wednesday, Liu also had talks with his Vietnam counterpart and met think tanks and media in Vietnam, Xinhua said.