Annan on Tuesday said he would await the return of political envoy al-Akhdar al-Ibrahimi from Baghdad to get a fuller picture of the troubles, but added that the dangers on the ground made a massive UN return impossible.
"For the foreseeable future, insecurity is going to be a major constraint for us. So I cannot say right now that I am going to be sending a large UN team," he said.
"Everybody knows protection is absolutely crucial for the return of our staff and for their effectiveness," Annan added.
"For the foreseeable future, insecurity is going to be a major constraint for us. So I cannot say right now that I am going to be sending a large UN team"
UN had withdrawn its international staff last October after a bomb attack on its Baghdad headquarters left 22 people dead.
But Annan in recent times had agreed to help Iraqis plan for an interim government, expected to take over from the US-led occupation forces on 30 June.
He dispatched al-Ibrahimi earlier this month to try to negotiate an agreement with the various Iraqi factions, as well as a separate election team to help prepare for national polls, expected by the end of January.
But UN officials say the work of the teams has been limited by worsening security and that the teams have only rarely left the so- called Green Zone, the headquarters of the occupation authority in central Baghdad.
"Given the deteriorating situation and the violence on the ground, even that task has been rather difficult," Annan explained.
Annan said the 30 June handover date was unlikely to be postponed, but underlined that continuing violence was posing problems.