Foreign Minister Taro Aso and U.S. Ambassador to Japan Thomas Schieffer jointly demanded Saturday that North Korea stop its apparent preparations to launch a long-range ballistic missile, calling it a "very provocative" act and warning such a move would further isolate it from the rest of the world.

After an evening meeting at the Foreign Ministry, Schieffer told reporters Washington will consider "all options" should Pyongyang ignore the warning, hinting at some sort of sanctions against the reclusive state if it launches the missile, which is believed to be a Taepodong-2. "We take (the indications of an impending missile launch) very seriously," Schieffer said. "This is very grave and provocative action."

According to the Defense Agency's annual defense policy report, the Taepodong-2 missile has a range of 3,500 to 6,000 km. This would allow them to reach as far as Alaska.

Schieffer called on North Korea to halt launch preparations and return to the six-party talks, the stalled dialogue framework among the U.S., Japan, China, Russia and South and North Korea to discuss Pyongyang's nuclear program.

Asked if the U.S. believes the missile was ready for launch, Schieffer said the U.S. is not sure, but there are indications that the preparatory actions are taking place.

"They are taking steps, (but) we don't exactly know how close they are to (a launch)," he said. After their meeting, Aso separately told reporters that Tokyo has already conveyed a warning message to Pyongyang through diplomatic channels in Beijing, urging it to stop the launch preparation. In 1998, North Korea test-fired a Taepodong-1 missile, which flew over Japan and landed in the Pacific Ocean, sparing security fears.