Restrictions on movement will also be extended to protect voters, who will be electing a transitional national assembly amid continuing violence.
The political situation has continued to worsen in the run-up to the polls – the first since Saddam Hussein was ousted.
Insurgents have carried out a series of attacks on Iraqi security forces and US troops.
Local security forces will provide the bulk of the protection for the polls but US troop levels will reach their highest level – at about 150,000.
