U.S. Secretary of State Rex Tillerson has called on China to do more to pressure North Korea over its nuclear weapons and ballistic missile programs.
Speaking after talks in Washington on June 21 between high-ranking U.S. and Chinese officials, Tillerson said "China understands the United States regards North Korea as our top security threat."
Tillerson noted that Beijing has a responsibility to pressure North Korea economically and diplomatically.
He called for increased efforts to block sources of finances for Pyongyang and to force North Korea to abide by United Nations Security Council resolution on its nuclear and ballistic missile programs.
U.S. Defense James Mattis said after the talks that the death this week of a U.S. student who was imprisoned by North Korea was evidence of a "regime that provokes and provokes and provokes."
Mattis said both the United States and China share the goal of a denuclearized Korean Peninsula.
Mattis also said that both sides at the talks had agreed to expand military-to-military contacts -- including exchanges of officers.
Tillerson and Mattis were hosting Chinese State Councilor Yang Jiechi and General Fang Fenghui, the chief of joint staff of the People’s Liberation Army.
The talks came a day after U.S. President Donald Trump said Chinese efforts to convince North Korea to curb its weapons programs had failed.
Washington has also increased its criticism of North Korea after the death of the U.S. student, Otto Warmbier, shortly after he was released from North Korea.
Warmbier arrived home last week in a coma following more than 17 months in North Korean captivity. The circumstances of his coma and death remain unclear.
The U.S. State Department said on June 20 that Washington holds Pyongyang accountable for its treatment of Warmbier, and urged North Korea to free three other U.S. citizens who are currently in detention in the country.
Trump called Warmbier’s death a "total disgrace."
Warmbier was sentenced in March 2016 to 15 years in prison with hard labor for trying to steal a propaganda sign from a hotel.
Pyongyang said Warmbier contracted botulism, a rare illness that causes paralysis, after his trial, and had been in a coma since he was given a sleeping pill.
However, U.S. doctors said he had suffered a "severe neurological injury" of unknown cause.
Warmbier’s family have declined a post-mortem examination.
On June 20, a U.S. official said U.S. spy satellites had detected movements at north Korea’s nuclear test site near a tunnel entrance.
But the official said it was unclear if North Korea was preparing for a new nuclear test to coincide with the June 21 talks in Washington with Chinese officials.
North Korea last tested a nuclear bomb in September. It has repeatedly conducted missiles tests since then and has vowed to develop a nuclear missile capable of striking the U.S. mainland.
The State Department also said the June 21 talks covered issues such as counterterrorism and territorial rivalries in the South China Sea.
With reporting by Reuters, AP and dpa