ANKARA (Reuters) - Turkey will hold a referendum by next May on constitutional changes expanding the powers of President Tayyip Erdogan, who survived an attempted July coup and is now conducting a purge of suspected participants, from generals to judges and journalists.

Deputy Prime Minister Nurettin Canikli told A Haber television in an interview on Friday that parliamentary and presidential polls would then be held in 2019, cementing a radical change in power structures long sought by Erdogan.

“The referendum looks like it could be held around March or April, but it could also be pushed to May,” Canikli said, ruling out any early election before 2019.

A senior official from the ruling AK Party, in power since 2002, said the party would submit its proposal on the constitutional changes to parliament on Saturday.

Erdogan has turned a largely ceremonial presidency into a powerful platform at a time of domestic upheaval by drawing on his own unrivalled popularity. The AK Party now seeks a strong executive presidency that while formalizing his personal powers could avert any relapse into the fractious coalition governments of the 1990s.

AKP officials refer to the current system as a “de facto presidential system”.

Opponents, however, fear the change will bring increasing authoritarianism to a country already under fire from Western allies over its record on rights and freedoms, especially after purges following the coup attempt.

Canikli said he expected all members of the AKP to vote in favor of the proposal and that the nationalist MHP opposition would also support the bill.

“The leaders of the AKP and MHP are in agreement at the moment, the following period is one for the commission and general assembly,” Erdogan told reporters after Friday prayers.

Any constitutional change needs the support of at least 330 deputies in Turkey’s 550-seat assembly to go to a referendum. The AKP has 316 lawmakers eligible for voting, and the MHP 39.

On Monday, MHP leader Devlet Bahceli was cited by broadcaster CNN Turk as saying there were no issues with the draft of the bill.