North Korea said Saturday preparations for the launch were complete and liftoff was imminent, as U.S., Japanese and South Korean warships with radar plied waters near the communist nation to monitor what they fear is a long-range missile test.

"Preparations for launching 'Kwangmyongsong-2,' an experimental communications satellite, by carrier rocket 'Unha-2' have been completed at the satellite launching ground in the east coastal area," the state-run Korean Central News Agency reported, citing information from the Korean Committee of Space Technology. "The satellite will be launched soon."

North Korea vowed to carry out its controversial rocket launch between Saturday and Wednesday.

Weather conditions Saturday, however, may have caused a delay of the launch.

"We thought the launch was likely today, but weather conditions at the rocket base may not have been favorable," South Korea's Yonhap news agency quoted a presidential Blue House official as saying.

South Korea's meteorological agency said the location of the missile base was under mostly cloudy skies with occasionally strong winds.

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Two sources told FOX News the launch could occur "any minute." The predictions of an early launch was partly based on the fact that the U.S. would be less ready to monitor the launch the sooner it stars.

The U.S. and North Korea's neighbors suspect the launch is a cover for testing the regime's long-range missile technology.

North Korea is about a half day ahead of the United States. Its stated time window for the launch is 10 p.m. to 3 a.m. EDT.

U.S. officials urge caution about calling the launch, if it happens, a "success" or "failure" because, short of an explosion on the launch pad, almost any result will yield the North Koreans useful data, particularly for future missile sales to other countries or entities.

The North has said its rocket will fly over Japan and its first stage is expected to fall in waters less than 75 miles from Japan's northwestern shore, according to coordinates the government in Pyongyang provided to U.N. agencies. The other zone where the second stage should fall lies in the middle of the Pacific between Japan and Hawaii.

China, North Korea's closest ally, said it was working to avert a launch. Beijing has tried to persuade North Korea on several occasions and will attempt to do so "to the last minute," Chinese President Hu Jintao told his South Korean counterpart, Lee Myung-bak, on Friday in London, according to the South Korean president's spokeswoman, Lee Dong-kwan.

A senior administration official told reporters in France for the NATO summit that the president is "mindful of the intense interest" in the expected intercontinental ballisitc missile launch by the North Korean government - a move the Obama administration says would violate a 2006 U.N. Security Council resolution and will, if it happens, trigger a move to punish North Korea with new U.N. sanctions.

The official said such a missile launch would have profound consequences for "our national security and global security."

Obama has said the planned launch has put "enormous strains" on international talks over North Korea's disputed nuclear ambitions.

The U.S. will "take appropriate steps to let North Korea know that it can't threaten the safety and security of other countries with impunity," he said.

Stephen Bosworth, the U.S. envoy on North Korea, said the communist nation would face consequences if the launch goes ahead. But he also said he is prepared to go to Pyongyang whenever it would be useful in order to restart international negotiations aimed at getting North Korea to abandon its nuclear program.

FOX News' James Rosen and Major Garrett, Reuters and The Associated Press contributed to this report.