US President George W Bush and prime ministers Tony Blair of Britain and Jose-Maria Aznar of Spain will hold a summit on Iraq in the Azores islands on Sunday.
Preparations for the emergency summit were made as the three countries struggle to gain support for a new UN Security Council resolution to pave the way for war.
France and Russia have vowed to veto any resolution authorising force and many observers doubt that a resolution would get the necessary nine votes to be passed anyway.
EU foreign policy chief dismissed concerns that Spain and Britain was forming an alliance with a country outside the EU.
"I don't think [it] will cause damage to the European Union," he said, while insisting that the international community would "have to wait for the results".
Today's announcement comes after the US and Britain again failed last night to win over neutral nations a the UN Security Council.
The White House still hopes to persuade six undecided nations on the council but US Ambassador Mr John Negroponte and British Ambassador Mr Jeremy Greenstock decided not to bring their resolution to a vote on today, because of lack of support.
While France has indicated it will give consideration to new British compromise proposals, they again indicated today they would veto any resolution authorising an attack.
US Secretary of State Mr Colin Powell has warned that Washington could pull the resolution entirely, and today's announcement appears to increase the possibility.
"The options remain, go for a vote and see what members say or not go for a vote," Mr Powell told a US congressional committee. "But . . . all the options that you can imagine are before us and [we will] be examining them today, tomorrow and into the weekend".
With over 250,000 US and British troops poised to invade Iraq, President Bush maintains he will begin a war without UN backing if necessary. He added to the US firepower yesterday, sending B-2 stealth bombers to the region.
The latest round of four-hour Security Council consultations last night were again deadlocked, with undecided members trying to come up with their own proposals.
Mexico, Chile, Pakistan and Guinea criticised the resolution and spoke in favour of proposals that would not immediately trigger war, diplomats said.
Agencies