The deal, valued at up to $111 million, would boost Turkey's self-defense as well as regional security and its ability to operate with U.S. forces and other NATO members, a Pentagon notice to lawmakers said.

Ankara has been seeking the helicopters to replace those lost in its long struggle against PKK terrorists.

Turkey last week launched air and ground assaults on terrorists in northern Iraq, vowing to exact "great revenge" after 24 Turkish troops were killed on October 19 in one of the deadliest attacks in years.

Under the administration's plan, the Marines would get two new, late-model Textron Inc Bell AH-1Z SuperCobras in exchange for the three, twin-engine AH-1W aircraft that would be transferred to Ankara, a congressional official told Reuters.

The Pentagon's Defense Security Cooperation Agency said the sale's effect on U.S. Marine Corps "readiness" would be mitigated by using the proceeds for the Corps' SuperCobra upgrades program.

Such sales from the U.S. military's current inventory are extremely rare. The United States and Turkey have a long tradition of military cooperation, both bilaterally and inside the North Atlantic Treaty Organization.

Turkey already uses the AH-1W helicopter, the backbone of the U.S. Marine Corps attack helicopter fleet, having bought 10 of them in the 1990s. The proposed sale would enhance its ground defense capabilities, said the notice, which is required by law and does not mean a sale has been wrapped up.

Turkey also would get seven General Electric Co T700-GE-401 engines, six installed on the aircraft and one spare as part of the proposed deal, the security agency said.