Bhutto had planned to leave late Thursday night, but the trip was delayed in a mix-up over her passport, spokesman Farhatullah Babar said.

Babar said she had to return from the airport because she was carrying her old passport, which had expired.

"She left this morning," he said, adding that she would stay in Dubai for three or four days.

Bhutto, who returned to Pakistan from eight years in self-exile on October 18, is leading her opposition party into the January 8 general elections, but has said she may boycott the vote if it is not free and fair.

Her October homecoming parade in the southern city of Karachi was targeted by a suicide bombing that killed 139 people.

Two weeks later she left for Dubai to see her children and ailing mother, but returned home almost immediately after President Pervez Musharraf declared a state of emergency in Pakistan on November 3.