Media reports from South Korea and the United States said North Korea appears to be preparing to launch an inter-continental missile.
A report Tuesday by Yonhap news agency quoted an intelligence source as saying that North Korea has been moving equipment similar to its long-range Taepodong 2 missile, which the North unsuccessfully tested in 2006.
The source said it will likely take North Korea about two months to prepare for the launch.
The French news agency, AFP, quoted an anonymous U.S. official who also said there are signs the North is preparing for a Taepodong 2 launch. But, the official added that it is unclear whether Pyongyang would go through with the launch.
A spokesman for the U.S. State Department told reporters in Washington Tuesday that any North Korean ballistic missile test would be a provocation.
Robert Wood refused to comment on intelligence matters, but stressed that North Korean missile activities and programs were a concern to the region.
On Monday, the North said it will not dismantle its nuclear weapons program until U.S. nuclear weapons in the South also are dismantled.
Seoul and Washington have denied the presence of any atomic weapons in the South.
Also Monday, South Korea's Foreign Ministry said Russia will host the next meeting of six nations involved in North Korea's nuclear disarmament talks.
South Korea said the meeting does not represent formal negotiations. The six-party talks are in a stalemate over ways to verify North Korea's declared nuclear activities.
Some information for this report was provided by AFP and AP.