North Korea has brought forward the potential date of a controversial “satellite” launching to as early as Sunday, regional governments say.
Pyongyang formerly said the launch would happen between 8-25 February.
World powers, which say it is for testing a ballistic missile, a cover have condemned the planned launch.
The estimated flight path of the rocket remains the same and North Korea failed to tell international organisations of any changes in its strategy, said South Korea’s defence ministry.
The South 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.
North Korea has provoked international criticism using a fourth nuclear bomb test on 6 January.
A launching in the coming weeks would make up another important violation of UN Security Council resolutions banning the state from carrying out any nuclear or ballistic missile tests.