Japan has warned it will lodge a "fierce" protest with the United Nations Security Council if North Korea test-fires a long-range missile.
North Korea's missiles are based on Soviet technology
The untested Taepodong-2 is believed to have a range of up to 6,000km (3,728 miles) with a light payload, allowing it to reach parts of the United States.
North Korea reportedly ordered its people to raise the state flag and expect a television message on Sunday.
But the scheduled time passed without an address from the government.
Japanese Defence Agency officials concluded that a launch was not imminent, but that monitoring would continue, Japan's Jiji Press news agency reported.
The Korea Central News Agency later issued a statement in which it criticised the attitude of the US and Japan towards North Korea.
"The Korean army and people will do their best to increase the military deterrent with sharp vigilance to cope with the moves of the US, which is hell-bent on provocations for war of aggression on the DPRK ( Democratic People's Republic of Korea)," the statement said. No mention was made of a missile test.
'Signs of activity'
Earlier, Japanese Foreign Minister Taro Aso had said Tokyo could impose sanctions on North Korea in response to a test, and he stressed that the necessary Japanese legislation already existed.
"We've put together measures that would allow us to legally respond, and what comes next is implementing them," he added.
The report that North Koreans have been told to expect a message on Sunday came in a Japanese newspaper, Sankei Shimbun, which quoted unnamed Japanese government sources.
However, speculation has been high that the North is preparing for a test.
South Korean daily Chosun Ilbo reported that booster rockets had been loaded onto a launch pad and 10 fuel tanks moved to the site in the north-east of the country in preparation for a launch.
The information came from US and South Korean satellite images of the site, the daily said, citing an unnamed government official.
North Korea last tested a long-range missile in 1998, when it fired the Taepodong-1 missile, with a range of 2,000km, over northern Japan. The missile landed in the Pacific Ocean.
Diplomats say that North Korean technicians are going through the same procedures undertaken before the test in 1998.
Range estimates published by the Federation of American Scientists give the Taepodong-2 between 3,500km and 6,700km.
If this is confirmed, it would have the potential to hit Alaska.