Turkish President Recep Tayyip Erdogan has approved a constitutional reform bill, according to his office, in a move paving the way for a referendum on an amendments package that seeks to extend his powers.

The move on Friday came weeks after Turkey's parliament approved a new 18-article constitution to create an executive presidency along the lines of that in the United States and France.

The referendum "is planned to take place on April 16", deputy prime minister Numan Kurtulmus said in comments broadcast on state-run TRT television.

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The changes would enable the president to issue decrees, declare emergency rule, appoint ministers and top state officials and dissolve parliament - amendments that the two main opposition parties say strip away balances to Erdogan's power.

The proposed constitution, which would create an executive presidency for the first time in modern Turkey, also foresees the creation of vice presidents and the abolition of the office of prime minister.

Erdogan says the changes will provide stability at a time of turmoil and prevent a return to the fragile coalitions of the past.

Yet his opponents fear they may eventually bring Turkey under a one-man rule.

"We are about 60 days away from the referendum," Al Jazeera's Sinem Koseoglu, reporting from Istanbul, said.

"For now, public polls show that the 'Yes' campaigners and the 'No' campaigners are almost at the same level."

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If the changes are passed in the referendum, Turkey would head to general and presidential elections together in November 2019 - and the proposed powers would be granted to the president elected.

The bill indicates a person can be elected president for two five-year terms.

Erdogan's existing time as president will not be counted. If the legislation is approved in the nationwide vote, it could pave the way him to remain in office until 2029.