SEOUL, South Korea — North Korea said Monday the missile it launched over the weekend was a new type of long-range ballistic rocket that can carry a heavy nuclear warhead.

North Korean propaganda must be considered with wariness, but if confirmed, the claim marks another big step forward in the country’s escalating efforts to field a nuclear-tipped missile capable of reaching the U.S. mainland. Outside experts don’t believe the North can do that yet, but each new test pushes them closer to the goal.

The launch Sunday is an immediate challenge to South Korea’s new leader, a liberal elected just five days earlier who expressed a desire to reach out to North Korea. The country’s push to boost its weapons program also makes it one of the Trump administration’s most urgent foreign policy worries.

The missile flew for half an hour and reached an unusually high altitude before landing in the Sea of Japan, the South Korean, Japanese and U.S. militaries said. Tokyo said the flight pattern could indicate a new type of missile.

North Korea’s official Korean Central News Agency called the missile a “new ground-to-ground medium long-range strategic ballistic rocket Hwasong-12” that’s “capable of carrying a large-size heavy nuclear warhead.” Leader Kim Jong Un was said to have witnessed the test and “hugged officials in the field of rocket research, saying that they worked hard to achieve a great thing,” according to KCNA.

The launch jeopardizes new South Korean President Moon Jae-in’s willingness to talk to the North, and came as U.S., Japanese and European navies gather for joint war games in the Pacific.

“The president expressed deep regret over the fact that this reckless provocation … occurred just days after a new government was launched in South Korea,” senior presidential secretary Yoon Young-chan said. “The president said we are leaving open the possibility of dialogue with North Korea, but we should sternly deal with a provocation to prevent North Korea from miscalculating.”

Moon, South Korea’s first liberal leader in nearly a decade, said as he took his oath of office last week that he’d be willing to visit the North if the circumstances were right.

The U.N. Security Council will hold closed consultations about the launch on Tuesday afternoon, according to the U.N. Mission for Uruguay, which holds the council presidency this month.

U.S. Ambassador Nikki Haley said on ABC television that the U.S. has been working well with China, Pyongyang’s closest ally, and she raised the possibility of new sanctions against North Korea including on oil imports.

The Security Council has adopted six increasingly tougher sanctions resolutions against North Korea.

President Trump’s administration has called North Korean ballistic and nuclear efforts unacceptable, but it has swung between threats of military action and offers to talk as it formulates a policy.

While Trump has said he’d be “honored” to talk with leader Kim Jong Un under favorable conditions, Haley seemed to rule out the possibility. “Having a missile test is not the way to sit down with the president, because he’s absolutely not going to do it,” she told ABC.

Japanese officials said the missile flew for about 30 minutes, traveling about 800 kilometers (500 miles) and reaching an unusually high altitude of 2,000 kilometers (1,240 miles).  South Korea’s Joint Chiefs of Staff said it was launched from near Kusong, in North Phyongan province.

The U.S. Pacific Command said that “the flight is not consistent with an intercontinental ballistic missile,” a technology the North is believed to have tested clandestinely by launching rockets to put satellites in orbit.

David Wright, co-director of the Global Security Program at the Union of Concerned Scientists, said the missile could have a range of 4,500 kilometers (about 2,800 miles) if flown on a standard, instead of a lofted, trajectory – considerably longer than Pyongyang’s current missiles. He said Sunday’s launch – the seventh such firing by North Korea this year – may have been of a new mobile, two-stage liquid-fueled missile North Korea displayed in a huge April 15 military parade.

Japanese Prime Minister Shinzo Abe told reporters that the launch was “absolutely unacceptable” and that Japan would respond resolutely.

The White House took note of the missile landing close to Russia’s Pacific coast and said in a statement that North Korea has been “a flagrant menace for far too long.”

The statement said Washington maintains its “ironclad commitment” to stand with its allies in the face of the serious threat posed by North Korea. The latest “provocation” should serve as a call for all nations to implement far stronger sanctions against the North, it said.

Outside militaries and experts will closely analyze what the North fired. While Pyongyang regularly tests shorter-range missiles, it is also working to master long-range missiles.

Japanese Defense Minister Tomomi Inada suggested the missile might have been on a “lofted” trajectory, meaning it could fly a flatter path and have a far longer range. Japan’s Kyodo News agency, citing unidentified sources, said the missile may be capable of reaching 4,000 kilometers (2,500 miles) at a normal trajectory.

Italian Premier Paolo Gentiloni said the G-7 summit his country is hosting later this month would discuss how to deal with the risk North Korea’s missile launchings pose to global security.

“It’s a serious problem for global stability and security, and I’m convinced that the upcoming G-7, in friendship, will contribute to resolving this issue,” he said in Beijing.

The launch came as troops from the U.S., Japan and two European nations gather near Guam for drills that are partly a message to North Korea. The USS Carl Vinson, an aircraft supercarrier, is also engaging with South Korean navy ships in waters off the Korean Peninsula, according to Seoul’s Defense Ministry.