By Deborah Haynes, security and defence editor
The US may ask the UK to station American refuelling aircraft at a British base in Cyprus as Donald Trump weighs up whether to join Israel's war against Iran.
American B-52 bombers and jets are already deployed to Diego Garcia, a British base in the Indian Ocean, as part of a massive expansion of US firepower in the region.
However, it is not thought that conversations have taken place yet about pre-positioning B-2 stealth bombers at Diego Garcia. These US warplanes are armed with bunker busting bombs big enough to reach Iran's Fordow nuclear site, built deep into a mountain.
Under long-standing rules, the UK must grant permission to the US to use Diego Garcia for military operations.
The White House will need Britain's green light to be able to launch bombing raids against Iran from the site.
It is not clear whether that request has been made or what the answer would be.
Sources indicated that they did not believe President Trump had made a decision about whether to strike Iran, but they are preparing for all eventualities.
What is the current deployment?
British troops based in small numbers across the region, including Iraq, Bahrain and the RAF base at Akrotiri in Cyprus, are on alert in case the fighting spreads.
Any move by President Trump to bomb Iran could prompt the Iranian military to strike American, British and other allied targets across the Middle East.
Bolstering its defences, the British government has sent additional Typhoon jets to Akrotiri 鈥� taking the number to 14 along with two tanker aircraft, it is understood.
More British warplanes may also be deployed.
The US military has already sent tanker aircraft 鈥� which are used to refuel fighter jets mid-flight 鈥� to Spain and Greece and may also request to use the Royal Air Force base at Akrotiri in Cyprus.
An American aircraft carrier is also expected to arrive in the region within the next five to seven days. Three US fast jet squadrons have already been deployed.
The huge array of military strength is currently in a defensive posture, designed to deter Iran from striking against US interests. However it could be turned into an offensive force.