Iraq has threatened that it might take "unconventional" action on Friday night against US-led coalition forces approaching Baghdad.
"Tonight we will carry something non-conventional against them,not necessarily military," Iraqi Information Minister Mohammed Saeed al-Sahaf told a news conference.
"We will do something that will be a great example for these mercenaries," he said.
It was not clear what he meant by "unconventional". "I am not revealing a secret," Sahaf said.
US-led forces have been on alert for possible Iraqi use of biological or chemical weapons, which Baghdad denies it possesses.
It is difficult for the U.S. forces that are surrounded in Saddam airport to leave Baghdad alive, Sahaf said.
But he later said that Iraq will not use weapons of mass destruction.
Sahaf's remarks were made after US troops claimed they had occupied Saddam International Airport on the outskirts of the capital. He said the airport will become a "graveyard" for "American villains," referring to coalition troops.