Anti-war protestors have warned of the danger of any attack on Iran, at the fourth annual conference of the Stop the War Coalition.
About 400 delegates gathered at Euston Road, north-west London, to finalise plans for another protest against the UK's involvement in the Iraq conflict.
Campaign for Nuclear Disarmament chair Kate Hudson called for awareness of the "danger" of attacking Iran.
Veteran campaigner Tony Benn praised the coalition for its "wide alliance".
Mr Benn said the "lies and immorality and cost of this war" should be central at the next election.
March in Hyde Park
Kate Hudson said: "Today we are calling for an end to the occupation of Iraq, but we must equally raise the call to build mass popular awareness of the danger - don't attack Iran."
The coalition is planning another national demonstration in London on 19 March to demand that UK troops be brought home.
A march from Hyde Park will be followed by a rally in Trafalgar Square.
On Tuesday, a "die-in" will take place in Parliament Square to mark the second anniversary of the anti-war march joined by more than one million people.