Lolita C. Baldor

Associated Press

Washington — The U.S. military expects another North Korean missile launch in the next several days, American defense officials said Tuesday.

The officials said the U.S. has increased its surveillance over the isolated, communist country and has seen a North Korean missile launcher moving around, as well as construction of VIP seating in the eastern coastal city Wonsan.

The officials, who weren’t authorized to discuss the matter publicly and spoke on condition of anonymity, said the new surveillance includes satellites, drones and other aircraft.

North Korea, which is banned by the U.N. from conducting long-range missile tests, says it is in the final stages of developing an intercontinental ballistic missile, fitted with a nuclear warhead, that could reach the U.S. mainland. Experts say the North may be able to reach such capability in the next couple of years.

Earlier this month, Pyongyang fired off four ballistic missiles into the Sea of Japan, reportedly reaching within 200 kilometers (120 miles) of Japan’s shoreline.

On Saturday, it conducted a ground test of a new type of high-thrust rocket engine, which it hailed as a breakthrough for the country’s space program. Leader Kim Jong Un said the test was to determine the engine’s thrust power, but weapons experts say such technology also has applications for the North’s ballistic missile program. The U.S. and other countries have often accused North Korea of using its space program as a cover for military advances.

The U.S. officials on Tuesday said it’s unclear what type of missile launch may be coming. North Korea previously has conducted tests in Wonsan of its medium-range ballistic Musudan missile.

North Korea has emerged as perhaps the Trump administration’s most pressing national security concern, and the latest surveillance information comes as the U.S. explores new diplomatic, security and economic measures to halt Pyongyang’s nuclear and ballistic missile programs.

White House press secretary Sean Spicer on Tuesday described the North Korean threat as “grave and escalating,” and a National Security Council official told a nuclear conference that the administration is conducting a high-priority review of North Korea policy.

Christopher Ford, senior director for weapons of mass destruction and nonproliferation on the NSC staff, said reviewers are considering a “full spectrum of possibilities.”

“There’s this enormously broad continuum, and we are looking at that entire conceptual space,” Ford told the Carnegie International Nuclear Policy Conference. He gave no concrete examples, but in an attempt to illustrate his point that the choices run the gamut, he said they range from “warm hamburger” to “war hammers.”

Visiting the Northeast Asia last week, Secretary of State Rex Tillerson threatened North Korea with tougher sanctions, more pressure and possible military action.

The North responded by saying it isn’t frightened by U.S. threats.

Associated Press writers Darlene Superville and Robert Burns contributed to this report.