Following PMQs, western officials said HMS Dragon was expected to sail from Portsmouth next week, with the warship currently being loaded with ammunition.
Two Royal Navy Wildcat helicopters, armed with Martlet missiles capable of shooting down drones, are expected to arrive in Cyprus separately and sooner.
A western official said that so far US bombers have not used the British bases of Diego Garcia or RAF Fairford – but said the UK was ready to accept them. The official said he expected them to arrive within the next few days.
Earlier, former Conservative Foreign Secretary Jeremy Hunt said he thought the prime minister had “made a big misjudgement” by not allowing the US to use British military bases for offensive strikes on Iran.
He told BBC Radio 4’s Today programme that international law was “not settled on this issue” and depended on whether there was an imminent risk of attack from Iran.
Hunt said the Americans had a significant role in defending Europe and in this situation, “to weaken our alliance with the United States was a big mistake”.
“President Trump is not interested in that rules-based order,” Hunt said.
“He’s said so absolutely explicitly. And we have to recognise the brute strength of the American military is something we depend on now in Europe and will depend on for at least a decade.”
Gen Sir Richard Shirreff, a retired British Army officer, said the UK “has got to focus on its interests” because “America has made it clear it’s not going to underwrite European security”.
Sir Richard, Nato’s former deputy supreme allied commander Europe, said it was in Britain’s interest to protect its military bases abroad.
“There is absolutely a case for getting involved,” Sir Richard said. “But I would not get involved in any way, shape or form in an operation where the end-stage is not clear.
“There is clearly no strategy and yet again we have an American president who has launched a war of choice with no clear understanding where this thing is going to end.”