"Even the American and Iraqi officials are sceptical about these groups, who they are and whether they represent and influence the resistance at the ground level," he told AFP.
He said some groups had asked to participate in a reconciliation conference being organised by the Arab League.
But the League has asked that they first declare a ceasefire for three months and arrange a spokesman with whom there can be dialogue that could also "reveal some identity of who these groups are," he added.
The conference, to be held in Cairo, has been delayed repeatedly since March and is now expected to be held the first week of August.
Meanwhile, Iraq said on Wednesday it had captured a Tunisian Al-Qaeda militant allegedly behind the February bombing of a revered Shiite shrine that unleashed a massive wave of sectarian violence.
Iraqi national security advisor Muwaffaq al-Rubaie said "we managed to capture Abu Qudama al-Tunisi, a Tunisian, recently and he has taken an active part in blowing up the Golden mosque."