The below is attributable to Spokesperson Heather Nauert:?
On June 7, Deputy Secretary of State John J. Sullivan met at the Department of State with Chinese Ambassador Cui Tiankai. During their meeting, they discussed the importance of the upcoming summit between President Trump and North Korean leader Kim Jong-Un, and reaffirmed the commitment of the United States and China to maintain sanctions on North Korea as mandated by relevant UN Security Council resolutions. The Deputy Secretary and Ambassador Cui also discussed the serious health incident affecting a U.S. official who served in Guangzhou. The Deputy Secretary thanked China for its commitment to ensuring the safety and security of all foreign diplomats in China. He also thanked China for its continued willingness to assist in the investigation of the incident.
Source: U.S. State Department.