China's import growth slowed faster than expected in April, as inbound shipments of commodities such as iron ore and copper weakened, while export growth more than halved, in line with a general cooling in demand for electronic gadgets.

Philippine President Rodrigo Duterte said on Thursday his telephone conversation this week with Chinese leader Xi Jinping to discuss the Korean peninsula crisis was at the behest of his U.S. counterpart, Donald Trump.

Chinese Vice Premier Wang Yang discussed China-U.S. economic ties on the phone with U.S. Treasury Secretary Steven Mnuchin and Commerce Secretary Wilbur Ross on Wednesday, the state-run Xinhua news agency reported.

The United States is negotiating with China on a possible stronger U.N. Security Council response - such as new sanctions - to North Korea's repeated ballistic missile launches, which the 15-member body normally condemns in a statement, diplomats said.

China on Wednesday urged all parties in the Korean standoff to stay calm and stop irritating each other.

U.S. President Donald Trump said on Thursday a major conflict with North Korea is possible in the standoff over its nuclear and missile programs, but he would prefer a diplomatic outcome to the dispute.

China has told the U.S. it had warned North Korea that it would impose unilateral sanctions should Pyongyang carry out another nuclear test, according to U.S. secretary of state Tillerson.

Rather than easing tensions, deploying the missile defense system undermines trust among all parties, China's top diplomat in the U.S. says.

The missile defense system will be operational "in the coming days."

The Trump administration said on Wednesday it aimed to push North Korea into dismantling its nuclear and missile programs through tougher international sanctions and diplomatic pressure, and remained open to negotiations to bring that about.