The UK will still not be "directly involved" in the strikes and Downing Street said, “the principles behind the UK’s approach to the conflict remain the same."
Britain had previously allowed US forces to use its bases for operations to prevent Iran from firing missiles that put British interests or lives at risk.
A Downing Street spokesperson said that ministers agreed on Friday that bases could now be used for “US defensive operations” to target “capabilities being used to attack ships in the strait of Hormuz”.
They add that “ministers underlined the need for urgent de-escalation and a swift resolution to the war."
Earlier Friday, Iran’s foreign minister, Abbas Araghchi, warned his British counterpart, Yvette Cooper, that the UK allowing the US to use British military bases would be treated as “participation in aggression” as he insisted on his country’s "right to self-defence."
“These actions will definitely be considered as participation in aggression and will be recorded in the history of relations between the two countries. At the same time, we reserve our inherent right to defend the country’s sovereignty and independence,” Araghchi said, according to a statement posted on his official Telegram channel.
The Iranian foreign minister said the US and Israel started the war while diplomatic negotiations were underway and condemned the “biased” response from Britain and other European countries towards what he described as “blatant aggression” in breach of international law.
He also pointed to the 28 February bombing of an Iranian girls’ school in Minab, in southern Iran, in which more than 165 people, mostly children, were killed, describing the attack as “cowardly."
Shortly after the call, PM Keir Starmer’s official spokesperson stated, "So our position is very clear. We didn’t participate in the initial strikes, and we’re not getting drawn into the wider war."
"We have authorised the US to use our bases for a specific defensive and limited purpose in response to Iran’s continued and outrageous aggression, and we’ve always said that this is the best way to eliminate the urgent threat and restore a path to diplomacy."
Later on Friday, the Ministry of Defence (MoD) confirmed in an operational update that the UK conducted defensive air patrols over Jordan, Qatar, the United Arab Emirates, and Bahrain last night.
Typhoon and F-35 aircraft, supported by Voyager air-to-air refuelling, carried out the patrols, explained the MoD.
The UK has more jets flying in the region than at any time in the last 15 years, while British pilots have now exceeded 700 flying hours, the MoD said.
There are 500 UK personnel supporting air defence activities across the UK’s bases in Cyprus, and the UK sent a small number of additional planners to US Centcom to help with planning and option development for ways to improve security in the Strait of Hormuz, it added.
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