In this image taken from a video, North Korean leader Kim Jong Un, center, reacts during the launch of four missiles. (KRT via Associated Press video)

The Trump administration turned up rhetorical pressure on North Korea on Tuesday, calling it an isolated and dangerous threat and underscoring the country’s commitment to defend Asian allies President Trump had criticized as free riders during the presidential campaign.

At the White House, press secretary Sean Spicer said Trump had assured leaders of Japan and South Korea, during phone calls Monday, of the “ironclad commitment to stand with Japan and South Korea in the face of the serious threat posed by North Korea.”

At the State Department, a spokesman used the first public press briefing since the administration took office to label North Korea a “pariah” and announce that the reclusive regime would be a central topic for Secretary of State Rex Tillerson during a trip to China, Japan and South Korea starting next week.

“Obviously given North Korea’s continuing provocative behavior and actions, the U.S. is actively engaged with its partners and allies in the region to address the threat posed by North Korea’s weapons programs,” State Department spokesman Mark Toner said.

The Trump administration canceled plans for unofficial talks between U.S. and North Korean representatives in New York this month, ending at least for now a back channel that has been used in the past to try to reassure Pyongyang that the United States does not plan to attack.

North Korea fired a ballistic missile last month in what was widely seen as a test of U.S. resolve, and on Monday fired four ballistic missiles into the sea off Japan’s northwest coast.

“Given North Korea’s recent behavior, we’re not at the point where we’re looking at direct engagement with them. We’re not rewarding that behavior in any way, shape or form,” Toner said.

“They’re increasingly becoming a pariah through this kind of behavior,” Toner said. “We’re pursuing tougher and tougher sanctions, but we’re also looking at other means to make that message clear to them.”

The White House is considering tougher missile defense systems as part of an ongoing review of diplomatic and military policy surrounding North Korea. The study was among the first undertaken by the new administration, which considers North Korean nuclear weapons capability a primary threat.

The Trump administration had shelved the regular daily State Department briefings in part to consolidate control of U.S. policy at the White House. The absence was one of the most visible signals that the Trump administration might try to reduce the role of the State Department in foreign policy and national security decisionmaking.

Tillerson’s upcoming trip sends mixed signals about his own profile and priorities in a new administration whose every move is scrutinized by foreign capitals for clues to U.S. plans and policy.

He will reaffirm the U.S. military pledge to defend Japan and South Korea, a bedrock of U.S. nuclear policy in Asia for decades that Trump had questioned as a candidate. He will reiterate to China that the United States is not planning to upend the separate decades-old “One China” policy governing Taiwan, which China considers a province.

But Tillerson is traveling without the usual symbolism of the big blue and white “United States of America” plane past secretaries of state have routinely used, and without the usual U.S. press corps. The State Department has said only that a smaller plane is more convenient and reliable, and that there is not room to bring reporters.

In China, where Tillerson will be first senior Trump administration official to visit, he will try to enlist greater Chinese help in deterring North Korea while calming Chinese government anger over the U.S. deployment of an anti-missile system to South Korea.

Chinese opposition to a system it sees as a potential threat could undermine Beijing’s willingness to lean on North Korea. Chinese economic and diplomatic influence is considered essential to reining in North Korea, which sees the United States as its principal enemy.

China threatened “necessary measures to safeguard our own security” in response to deployment of the THAAD anti-missile system. THAAD stands for Terminal High Altitude Area Defense.

“We’ve been very clear that a decision to deploy THAAD is as a defensive measure, in order to protect not only South Korea, but also our military who is stationed in South Korea,” Toner said.