DUBAI, June 4 (Reuters) - Turkish Airlines is advancing talks with Boeing for 150 737 MAX narrow-body jets and 75 widebody 787 planes, but a final decision hinges on engine price negotiations, Chairman Ahmet Bolat said on Tuesday.

In April, the carrier said it was negotiating with both Airbus and Boeing to buy 235 aircraft as part of its expansion plans, after placing an order for 355 jets with the European planemaker in December.

Bolat said talks are advancing with Boeing, even as Airbus remains in the race, but a final decision will depend on better pricing for CFM's LEAP engines, the sole provider for the 737 MAX planes.

"We could announce the Boeing order earlier but there is an engine issue. A decision depends on CFM's prices and that is why it will take a little longer," Bolat said, speaking on the sidelines of the International Air Transport Association's (IATA) annual meet in Dubai.

Bolat said the airline has made a counter proposal to CFM, a joint venture between GE and France's Safran, and is waiting to hear back.

The talks with Boeing come when the manufacturer is engulfed in a sprawling safety crisis made worse by a January mid-air panel blowout on a near-new 737 MAX plane.

Boeing is facing investigations by U.S. regulators, possible prosecution for past actions and slumping production of its strongest-selling 737 MAX jet.

Bolat, however, said he was confident Boeing will solve its problems, and that the planemaker was taking "strong steps and measures".

He said Turkish placed the 355-planes order with Airbus because it wanted to secure the fast-filling slots, and while it was still talking to the European planemaker for the new order, he wants to work with both manufacturers.

"We want to mitigate the risks, reduce the risks by using both products available in the market," he said. (Reporting by Aditi Shah; editing by Jason Neely and Sriraj Kalluvila)