Japan starts deploying Patriot missile defence system after North Korea threatened to fire ballistic missiles over the country.

The United States demanded that North Korea "must stop its provocative and escalatory behaviour" early on Saturday after President Donald Trump stepped up his warnings against Pyongyang and spoke with his Chinese counterpart Xi Jinping over the phone.

The U.S. military forces "stand ready" to safeguard Guam after North Korea threatened to fire ballistic missiles toward the American Pacific island territory, the White House said.

It said Mr. Trump "reassured" Guam Governor Eddie Calvo in a phone call that the U.S. military would "ensure the safety and security of the people of Guam, along with the rest of America."

During their separate call, Mr. Trump and Mr. Xi also hailed the adoption of a United Nations Security Council resolution targeting North Korean as an "important and necessary step toward achieving peace and stability on the Korean Peninsula," a White House statement read.

"The Presidents also reiterated their mutual commitment to denuclearization of the Korean Peninsula," it added, stressing the two leaders had an "extremely close relationship" that "will hopefully lead to a peaceful resolution of the North Korea problem."

"President Trump and President Xi agreed North Korea must stop its provocative and escalatory behavior," the statement read.

It said Mr. Trump looks forward to a "very historic" meeting with Mr. Xi in China later this year.

U.S. forces 'ready' to protect Guam

US military forces "stand ready" to safeguard Guam after North Korea threatened to fire ballistic missiles toward the American Pacific island territory, the White House said early Saturday.

During a ohone call to Guam Governor Eddie Calvo, Mr. Trump "reassured" him that "U.S.forces stand ready to ensure the safety and security of the people of Guam, along with the rest of America," a statement said.

It said White House Chief of Staff John Kelly spoke with Mr. Calvo separately in an earlier call.

Japan deploys missile defence

Japan started deploying the Patriot missile defence system after North Korea threatened to fire ballistic missiles over the country toward Guam, reports said.

The defence ministry started deploying the Patriot Advanced Capability-3 (PAC-3) system in Shimane, Hiroshima and Kochi in western Japan, which Pyongyang warned could be along its missiles' flight path, public broadcaster NHK said.

It was also to deploy the anti-missile system in neighbouring Ehime, NHK said.

Television footage showed military vehicles carrying launchers and other equipment for the surface-to-air system entering a Japanese base in Kochi before dawn.

While immediate confirmation of the reports was not available, Japan has in the past vowed to shoot down North Korean missiles or rockets that threaten to hit its territory.

The government hopes to complete deployment of the system in western Japan by Saturday morning, Kyodo News said, quoting defence ministry officials.

Yoshihide Suga, Japan's chief government spokesman, said earlier this week that Tokyo "can never tolerate" provocations from North Korea and the country's military, will "take necessary measures."

In 2009, a North Korean rocket passed over Japanese territory without incident or any attempt to shoot it down.

At the time North Korea said it was launching a telecommunications satellite, but Washington, Seoul and Tokyo believed Pyongyang was testing an intercontinental ballistic missile.