Tony Blair, George W Bush and Jose Maria Aznar are holding an emergency meeting to try and find a path to peace.
Some top lawyers have said a war might be illegal if the world leaders don't have the UN's support.
But Mr Aznar said backing from the UN would be good but it's not completely necessary.
'Come and check for weapons'
Iraq has invited the chief UN weapons inspectors to visit Baghdad "as quickly as possible" to check again for any weapons they shouldn't have.
France, Russia and Germany still want to give Saddam time to disarm.
A BBC correspondent says there's little hope of new peace plans but Monday's deadline for Saddam to prove he's disarming could be extended.
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