David Cameron has urged North Korea to step back from launching a rocket in breach of UN resolutions.
The nuclear-armed regime is due to fire a rocket imminently that it says is designed to put a satellite into orbit.
However, the US believes the launch is a cover for testing a ballistic missile and Japan has readied its anti-missile systems.
Speaking to BBC Radio 5 Live, Mr Cameron said he regarded the prospective firing as a breach of UN edicts.
"We need to send a very clear message to the North Korean leadership," he said.
"They are not even able to feed their own people and yet they seem to be able to put satellites in the sky.
"They have a very clear choice. This regime needs to take a different path if it wants to be able to engage with the world."