Citing the tense security situation and the need to ensure the greatest number of Iraqis are able to vote, the former Iraqi foreign minister told CNN on Sunday that the US-backed poll faced a major "dilemma".
"We either have good, real elections, or we're going to have elections which are not complete, in which vast segments of Iraqi population would be left out.
"And I think this would lead to even greater insecurity in the country," Pachachi cautioned.
The Iraqi politician said he was urging a delay because it would also enable discussions to take place with those groups which are "reluctant or unwilling" to participate in the planned January poll.
Asked if a delay would represent a victory to fighters and their political allies, Pachachi said: "I don't agree, because I think a short delay would give us a chance to speak to those who are reluctant" and persuade them to take part in a political process.
He added: "They have to be inclusive. Otherwise the elections will be questioned from the point of view of legitimacy."
Pachachi also said he was "anxious" to participate in an election.
In the face of such calls urging a poll delay, Washington and the country's Shia majority are continuing to say elections should go ahead on 30 January.