North Korea has brought forward the possible date of a controversial "satellite" launch to as early as Sunday, regional governments say.
The secretive state will launch the satellite-bearing rocket between 7-14 February, the Japanese government has said, according to reports.
Pyongyang previously said the launch would take place between 8-25 February.
The announcement was condemned by world powers, which say it is a cover for testing ballistic missile technology.
South Korea has warned the North that it will "pay a harsh price" if it goes ahead with its plan to launch the satellite.
Japan's defence minister said he had issued an order to shoot down any missile that threatened to fall on Japanese territory.
North Korea has already provoked international criticism this year with a fourth nuclear bomb test on 6 January.
UN sanctions against the state prohibit it from carrying out any nuclear or ballistic missile tests.