North Korea’s “spectacular” rocket launch shows it has made progress in its missile capabilities, Japan said on Wednesday, as Tokyo urged a divided U.N. Security Council to deliver a strong rebuke to Pyongyang.

Analysts said Sunday’s launch was effectively a test of a ballistic missile designed to carry a warhead as far as the U.S. state of Alaska. North Korea insists it put a satellite into space, claims dismissed by the U.S. military and South Korea.

Referring to footage of the launch, broadcast by North Korean state television on Tuesday, Japan’s Chief Cabinet Secretary Takeo Kawamura said it was unclear if the rocket carried a satellite. It soared over Japan during its 3,200 km (2,000 mile) flight that ended in the Pacific Ocean.

“It was launched spectacularly,” Kawamura told a news conference. “We can say that the launch took place in a way that was more advanced than previous ones.”

In the only previous test flight of the Taepodong-2, in July 2006, the rocket blew apart 40 seconds after launch. The rocket is designed to fly an estimated 6,700 km (4,200 miles).

The United States, Japan and South Korea say the launch violated Security Council resolutions banning the firing of ballistic missiles by Pyongyang, imposed after a nuclear test in 2006 and other missile exercises.

Kawamura reiterated Tokyo’s demand for a strong response from the U.N. Security Council.

Diplomats have said China and Russia would probably accept a Security Council warning to Pyongyang urging it to comply with U.N. resolutions and return to six-party talks aimed at dismantling North Korea’s nuclear arms programme.

But they would be opposed to a binding resolution intended to punish Pyongyang. The United States and Japan would like a resolution that expands existing financial sanctions.

“There have been informal talks between the permanent members of the Security Council and Japan, but we hear that China’s stance is firm,” Kawamura said.

“Our government is continuing to work with the United States to negotiate, aiming for a new resolution.”

China and Russia, as permanent council members, have veto powers and have made clear they would stop new sanctions.

“STRONG STEPS”

North Korea warned the U.N. Security Council on Tuesday that it would take “strong steps” if the 15-nation body took any action.

“If the Security Council, they take any kind of steps whatever, we’ll consider this is (an) encroachment on our sovereignty and the next option will be ours,” deputy ambassador Pak Tok Hun told reporters in New York.

“Necessary and strong steps will … follow that.”

Beijing, the nearest North Korea has to a major ally and concerned about the stability of its unpredictable neighbour, has said any U.N. reaction must be “cautious and proportionate”.

Diplomats from the permanent council members and Japan had planned to meet on Tuesday, but the meeting was postponed and it was not clear when it would go ahead.

Analysts said the launch showed North Korea had increased the range of its missiles, although it might be years from building one that could threaten the United States.

“North Korea has made technological advances, regardless of the success or failure of the launch,” said Rim Chun-taek, a professor in aerospace engineering at the Korea Advanced Institute of Science and Technology in Seoul.