One of the UK's two aircraft carriers has been placed on advanced readiness to sail from Portsmouth.
The crew of HMS Prince of Wales have been told they must be ready to leave in five days, defence sources said.
This may raise speculation the carrier could be deployed to the Mediterranean to help defend British interests threatened during the conflict in the Middle East.
Before this, the ship's "notice to sail" was 14 days.
On Saturday night, US President Donald Trump criticised Prime Minister Sir Keir Starmer for not sending carriers to the Middle East earlier.
