Apparently, the US asked for Baykar drones and for them to be produced in the US as well as putting engines for the Kaan on hold. What a strange world we live in:
Foreign Minister Hakan Fidan: “The USA believes that the technology produced by Baykar could be a production field for the USA. The USA is demanding Turkey’s advanced technology in this field. Turkey can now sell ammunition and weapons to the US market.”
"The CAATSA issue with the US must be resolved. They need to take steps for both the F-35 and the engines of KAAN. The license for KAAN’s engine is currently on hold. When there are restrictions with the US, this will push us toward other pursuits in the international system."
It's a habit for the US to push other countries to make TOT without US giving them any, they do it for their best allies like Japan and even Anglo allies like UK.
I know there's a pressure on them to modernize their air force so that it can protect itself until the Kaan enter service, and they refuse any negotiation that tell them to stop the project or their industrial capabilities -- there's a history for that like what the russians did to egypt, and even the US did that to other countries.
I'm not certain, but I think the engine is already licenses in sweden for the gripen, so the most real problem is Israel lobby.