Foreign Secretary David Lammy has urged Iran to take "the off-ramp" and return to the negotiating table.
Iran has vowed there will be "everlasting consequences" following US strikes at the weekend, intended to take out the country's nuclear programme.
Lammy said he had told Iran that it would be a "catastrophic mistake" for them to retaliate by firing at US bases, or by blockading the key shipping lane of the Strait of Hormuz.
Speaking to BBC Radio 4's Today programme, Lammy said he had told the Iranian foreign minister to take a message to the Iranian leadership to "get serious about their nuclear programme".
He added: "They have to get serious about the off-ramp that is being made available to them.
