CAIRO, Jan 26 (Reuters) - Egypt will hold a presidential vote before electing parliament, President Adly Mansour said on Sunday, reneging on a roadmap and increasing the likelihood that army chief General Abdel Fattah al-Sisi will be elected as head of state within months.

Parliamentary elections were supposed to happen first under the timetable agreed after the army deposed Islamist President Mohamed Mursi in July following mass protests against his rule.

"I have taken my decision to amend the roadmap for the future in that we will start by holding the presidential elections first followed by the parliamentary elections," Mansour said in a televised speech.

Critics have campaigned for a change of the roadmap, saying the country needs an elected leader to direct government at a time of economic and political crisis and to forge a political alliance before a potentially divisive parliamentary election.

Opponents say it risks creating a president with unchecked power. Were that Sisi, who is widely tipped to win, it would put the army back in a post controlled by military men until Mursi was propelled to office by the Muslim Brotherhood.

A new constitution voted in this month opened the way for a change in the order of the elections by leaving open the question of which should come first. (Reporting by Shadia Nasralla and Asma Alsharif; Editing by Michael Georgy and Louise Ireland)