London: British Prime Minister Theresa May has ordered British submarines in the Mediterranean to move within missile range of Syria in readiness for strikes against the Assad regime by the end of this week.

Whitehall sources said Britain was "doing everything necessary" to be able to fire Tomahawk cruise missiles from nuclear-powered submarines against military targets in Syria.

One source said that "if any action is going to happen, it is going to happen before Monday".

As of Wednesday night, May had not come to a final decision on whether Britain would join the US and France in any air strikes, but the Prime Minister wants to be able to act swiftly if and when she decides to join any offensive.