Trump, Abe say North Korea threat 'entered a new stage'

US President Donald Trump (R) and Japan's Prime Minister Shinzo Abe spoke by telephone after North Korea fired off four ballistic missiles

US President Donald Trump and Japanese Prime Minister Shinzo Abe warned Monday that the threat from North Korea had "entered a new stage," following another defiant missile test.

The two leaders spoke by telephone after North Korea fired off four ballistic missiles, in what Pyongyang provocatively called a training exercise for a strike on US bases in Japan.

"Japan and the United States confirmed" the launches violated UN Security Council resolutions and presented a "clear challenge to the region and international community," Abe told reporters in Tokyo.

They also agreed that "the threat has entered a new stage," Abe said.

The missiles traveled about 620 miles (1,000 kilometers) and three of them landed in waters close to Japan that are part of its exclusive economic zone.

North Korean weapons programs are rapidly proving to be the most prominent foreign policy question facing Trump's young White House.

The president -- who has little foreign policy experience -- has described North Korea as a "big, big problem" and vowed to deal with the issue "very strongly."

Intelligence officials believe that Pyongyang could be less than two years away from developing a nuclear warhead that could reach the continental United States.

Trump has baldly declared that "it won't happen!" but has yet to articulate how he proposes to neutralize the threat.

Diplomacy has stalled and military options remain fraught.

Monday's launches were the latest in a series of test-firings that have increased in tempo.

Last month, Abe's visit to Trump's Florida resort was marred by another North Korean missile test.

On that occasion social media posts showed Trump and Abe huddling with aides in a public dining room as they weighed how to respond.

As a presidential candidate, Trump had called into question a mutual defense pact with Japan, insisting Tokyo must pay its own way. He has since softened that rhetoric.

Abe said that "President Trump said the United States is 100 percent with Japan and he told me to convey his remarks to the Japanese people."

"He said he wanted us to trust him and the United States 100 percent," Abe added.