The Irish Anti-War Movement has planned a series of protests which will swing into action on the day war begins.
Shannon Airport will again be a focal point for protests, campaigners said yesterday.
On the day war begins, everyone is being asked to stop work for 10 minutes at midday.
"We want everyone to stop what they are doing - work, school, college, driving - and make some sort of public protest against the war," said Mr Richard Boyd Barrett, chairman of the Irish Anti-War Movement.
The Irish Anti-War Movement will hold a protest outside the US embassy in Dublin at 6 p.m. on the day war begins. People who live outside Dublin will be asked to protest in their town centre at the same time on that day.
Mass demonstrations will be held in Dublin, Galway, Belfast, Cork and Derry on the Saturday after war begins.
This action has been endorsed by SIPTU.
Mr Joe O'Flynn, SIPTU general secretary, said the union's stance was " a matter of conscience" and a show of solidarity with the people of Iraq.
He said any action against Iraq was "entirely premature and without justification" if it did not have UN approval.
SIPTU did not hold any favour for Saddam Hussein, but "a single superpower cannot decide on its own authority to be the police person of the world".
Mr O'Flynn said the threat that US companies would pull out of Dublin was "scare-mongering". Companies came to this State for the experienced workforce it offered, not for political reasons.
Ms Bríd Smith, the Socialist Workers' Party national secretary, warned that Shannon Airport would again be a "major focus point" by anti-war campaigners.
She said the threatened war was the result of the "ruthless logic of globalisation", and millions of people would be killed "on behalf of oil interests".
Supporters of the anti-war protests include the Peace and Neutrality Alliance, SIPTU, the NGO Peace Alliance, the Labour Party, the Green Party, Sinn Féin and the Socialist Workers' Party.
