Sir Keir Starmer has said he stands by his decision not to join the initial US-Israel strikes on Iran on Saturday, and said talks would be the best way forward.
At a Downing Street news conference, the PM said the UK had "the strength to stand by our values and our principles no matter the pressure to do otherwise".
The UK's longstanding position was that the best way forward was a "negotiated settlement with Iran where they give up their nuclear ambitions", he added, saying efforts should be made to "de-escalate" the conflict.
Sir Keir said the conflict could continue for "some time", as he announced the UK is sending four additional Typhoon fighter jets to Qatar.
US President Donald Trump has already criticised the prime minister for refusing to allow the use of UK bases in the initial strikes, and said he is "not Winston Churchill".
