"The United States' unilateral intervention in Iraq threatens international law and the role of the United Nations," Greenpeace said in a press release issued here.

"The (European) countries' leaders must impose on the US to come back to the negotiating table of international cooperation," it continued.

Greenpeace attempted to drive the point home with plans to send a large balloon with the slogan "Unite for Peace" written across its surface into the Athens sky.

The balloon inflated but its operators decided not to let it rise due to high winds, the group's local spokesman told AFP.

Around 120 government officials from 40 different European countries gather in Athens on April 16-17 for the signature of the EU enlargement treaty bringing 10 new member states from southern and eastern Europe into the EU.

UN Secretary General Kofi Annan, who is also present, will hold talks on the UN's role in the reconstruction of post-war Iraq.

SPACE.WIRE