He was speaking on Spain's SER radio and was responding to a question about statements by the Spanish government which based its justification for supporting the war in Iraq on UN claims that Iraq possessed the weapons.
Blix stressed that nowhere in his report had it contained such a claim.
He said that his team's last report had constantly underscored that as far as biological or chemical weapons or missiles were concerned, there were many question marks.
"It noted that many Iraqi statements were erroneous. That left open the possibility that there could have been some weapons, but nowhere did our report state that there were weapons," he said, according to a transcript of the interview released by SER radio.
Iraq had claimed to have weapons of mass destruction and had then said it had destroyed them, Blix said.
Spanish Prime Minister Jose Maria Aznar, whose right-wing Popular Party is seeking re-election next month, was one of the staunchest supporters of the US-led invasion and subsequent occupation of Iraq.
The opposition Socialists have not let up in pressing Aznar's government to explain its statements about the presence of weapons of mass destruction in Iraq.
Aznar said on television last February ahead of the US-led war in Iraq that the Iraqi regime had weapons of mass destruction and had links with "terrorist groups".
Under pressure from the opposition about the origins of the statements, especially after reports about mistakes in US and British intelligence, the Spanish government has said that it was only repeating what the UN said.