ANKARA (Reuters) - Turkey’s parliament has approved key measures allowing the president to be a member of a political party and issue decrees, part of a constitutional reform the opposition says will fuel authoritarianism.

The ruling AK Party, backed by the nationalist MHP, is pushing through legislation that President Tayyip Erdogan says will bring strong executive leadership needed to prevent a return to the fragile coalition governments of the past.

The three articles approved overnight set out parliament’s supervisory role, enable the president to retain ties with a political party and detail the president’s executive powers as head of state, including the power to issue decrees.

Their approval, announced on Friday, is a positive sign for the AKP, although the changes will need to pass in two more rounds of voting before the constitutional package as a whole is put to a referendum, expected in the spring.

The main opposition CHP and the pro-Kurdish HDP, the second largest opposition party, strongly oppose the changes.

The previous night, lawmakers from the AKP and CHP came to blows as tempers boiled over in debate on the bill, after which a ruling AK Party deputy warned elections would be held if it was not passed.

Erdogan himself floated the possibility of early elections on Friday, saying they were not desirable but “not unthinkable” if parliament became unable to do its job.

A CHP deputy said on Thursday his party would not shy away from such a move.

“Today instead of seeking such a regime change, we as the CHP give full support to an early election decision. We say bring it on,” Ozgur Ozel told the general assembly.

Under the planned changes, a president can be elected for a maximum of two five-year terms. The plans envisage presidential and general elections in 2019.

The 18-article bill needs the support of at least 330 deputies in the 550-seat assembly to go to a referendum. The AKP has 316 deputies eligible to vote and the MHP 39.

The articles passed overnight with the support of 340-343 lawmakers.