Turkey's ruling party named a loyal ally of President Recep Tayyip Erdogan as the new prime minister Thursday, May 19, with the incoming premier immediately vowing to "work in total harmony" with the strongman leader, AFP says.

The ruling Justice and Development Party (AKP) will officially appoint Transport Minister Binali Yildirim as its chairman Sunday, meaning he will automatically become Prime Minister.

Yildirim will replace Ahmet Davutoglu, who stepped down after a struggle with Erdogan, as the president seeks to concentrate more power in the presidential office.

"We will work in total harmony with all our party comrades at all levels, beginning with our founding president and leader," said Yildirim after being named party head, referring to Erdogan, AFP says.

The 60-year-old Yildirim is seen as one of Erdogan's closest longtime confidants and has served an almost unbroken stint from 2002 to 2013 as transport minister and then again from 2015.

The new prime minister's main task, observers say, will be to pilot a change in the constitution to transform Turkey from a parliamentary to a presidential system, placing more power in Erdogan's hands.

"And now it's time for the presidential system," Yildirim said earlier in May just after Davutoglu's resignation.