Turkey is planning to buy four more F-35 Joint Strike Fighters from the US, in addition to the two it had already ordered, the country's defence industry agency said.

"It has been agreed that four more F-35 planes will be procured in addition to the two previously ordered as part of a plan to buy a total of 100 new generation F-35 Joint Strike Fighters," the defence industry executive committee (SSM) said in a statement posted on its website.

The decision came after a meeting chaired by Prime Minister Ahmet Davutoglu for the first time under his rule to discuss key defence purchases.

Turkey has long planned to purchase 100 jets to replace its ageing F-4 and F-16 fleet, but increasing costs have hampered the acquisitions.

The Joint Strike Fighter, manufactured by Lockheed Martin, is the Pentagon's most expensive weapons programme ever.

The defence committee also agreed to "continue negotiations" over Turkey's plan to buy defence missile systems.

Turkey, key NATO member, announced in 2013 that it was entering negotiations with the China Precision Machinery Export-Import Corporation (CPMIEC) to acquire its first long-range anti-missile systems.

But the plan has deeply concerned the United States, which has already imposed sanctions on the Chinese firm for supplying arms to Iran and Syria in defiance of an embargo.

Ankara has since then asked other contenders -- European and American firms -- to renew their proposals.