The United States and Japan are united in their efforts to clamp down on North Korea's "growing threat," as the regime ramps up its nuclear drive and other belligerent efforts, the White House said Sunday.

During a phone call, President Donald Trump and Japanese Prime Minister Shinzo Abe "reaffirmed that the United States-Japan Alliance stands ready to defend (against) and respond to any threat or action taken by North Korea", the White House said in a statement.

It added that the pair expressed "unity with respect to increasing pressure on the regime to change its dangerous path."

During a separate phone call with Chinese President Xi Jinping, the White House said it was Trump who "raised the growing threat posed by North Korea's nuclear and ballistic missile programs."

"Both leaders reaffirmed their commitment to a denuclearized Korean Peninsula."

But the White House made no mention of possible discussions between Trump and Xi over disputed islands in the South China Sea, even though the call took place just hours after a US warship sailed near an island in the waterway.

Beijing termed the incident a "serious political and military provocation."

The destroyer, the USS Stethem, sailed less than 12 nautical miles from tiny Triton Island in the Paracel Islands archipelago, which is claimed by China as well as Taiwan and Vietnam, a US official told AFP.

On the call, Trump also "reiterated his determination to seek more balanced trade relations with America's trading partners," the White House said, a reference to the US administration's aggressive stance on trade matters, especially as concerns China.

- Pinning hopes on China -

The Trump administration has been growing increasingly exasperated with North Korean leader Kim Jong-Un's regime, which has staged a barrage of missile tests in recent months.

Trump had been pinning his hopes on China -- North Korea's main diplomatic ally -- to bring pressure to bear on Pyongyang, but declared last week that their efforts had failed.

He has presented sanctions as the best way to proceed with the hermit state, opting for that approach over dialogue with the regime.

During talks with South Korean leader Moon Jae-In -- who has pushed for a policy of engagement with Pyongyang -- on Friday, Trump called for a "determined response" to the North. But the pair failed to map out a joint strategy on how to handle North Korean threats.

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

There was also deep anger in the United States after Otto Warmbier, an American student who was detained in North Korea on a tourist trip around 18 months ago, was returned home in a coma earlier this month. He died several days later.

Source: AFP