US President Donald Trump discussed North Korea's nuclear program in separate phone calls with Japanese Prime Minister Shinzo Abe and Chinese President Xi Jinping on Sunday night.

The White House said in a statement that Trump and Abe had agreed to increase pressure on Pyongyang, reaffirming that "the United States-Japan Alliance stands ready to defend and respond to any threat or action taken by North Korea."

In the case of China, Trump raised the growing threat of North Korea's ballistic missile programs and "reiterated his determination to seek more balanced trade relations with America's trading partners."

Trump is set to meet with both leaders at the G20 summit in Hamburg, Germany on July 7-8.

Pressure on Beijing

Washington has been pressing Beijing - North Korea's main diplomatic ally - to do more to curb its rogue neighbor's nuclear and missile programs. Trump has become increasingly frustrated with the lack of progress on this front, and his reference to trade could indicate a willingness to take a tougher approach towards Chinese trade practices in the future.

Trump is mulling new tariffs on steel imports for national security reasons and plans to discuss his concerns at the G20. Such a move could severely affect the interests of major trading partner China.

The phone call with Xi took place hours after a US warship sailed near a disputed island in the South China Sea claimed by China, drawing a rebuke from the Chinese Ministry of Foreign Affairs. It wasn't clear whether the two leaders discussed the incident.

China's state media reported that Trump and Xi had discussed the "peace and stability of the Korean peninsula," without elaborating. According to a report broadcast on state television, Xi told Trump China had already made its position clear about certain "negative factors" that have affected Sino-US relations.

Trump: No more patience

North Korea has carried out a number of nuclear tests in the past year, ratcheting up tensions with its regional neighbors and the US.

During White House talks with South Korea's new president, Moon Jae-in, last week, the US president called on Asian powers to implement sanctions and demand North Korea "choose a better path and do it quickly."

"The era of strategic patience with the North Korean regime has failed, many years it has failed. Frankly, that patience is over," Trump said.

nm/rg (Reuters, AP, AFP)