By Humeyra Pamuk and Patricia Zengerle
(Reuters) - U.S. President Joe Biden's administration notified Congress on Monday of the planned sale to Turkey of avionics software upgrades for its current fleet of F-16 fighter aircraft, a deal valued at up to $259 million.
The deal, first reported by Reuters earlier on Monday, moves ahead with the sale of the modernization package for Turkey's aircraft, after leaders of U.S. congressional committees gave informal approval.
A larger agreement, NATO member Turkey's request to buy billions of dollars worth of F-16s, remains in limbo amid continuing opposition in Congress.
If it is cleared by Congress during the formal approval process, the package would be the first major military sale to Turkey that Congress has approved for years.
"Türkiye is a longstanding and valued NATO ally," a State Department spokesperson said in a statement. "The Biden Administration supports Türkiye’s efforts to bring the avionics of its F-16 fleet up to standard."
The spokesperson noted that the upgrade will improve the interoperability between Turkish and NATO systems by updating its communications and also provide upgrades to enhance safety measures such as a ground collision avoidance system.
The F-16 modernization deal follows Turkey approving Finland's accession to the NATO military alliance and signs of easing tensions between Turkey and neighbor Greece ahead of Turkish elections next month.
Lockheed Martin Corp will be the principal contractor on the deal.
The package is separate from the proposed $20 billion sale of new Lockheed Martin F-16 fighters and nearly 80 modernization kits that Turkey requested in October 2021.
The smaller package was approved after the administration pushed the lawmakers to approve it to send a "positive signal" to Ankara, according to one source familiar with the deal.
The approval does not mean the bigger sale will receive a green light from Congress as U.S. lawmakers are seeking assurances from Turkey on issues that go beyond the Nordic NATO expansion.
Those issues include easing tensions with Greece for good, refraining from an invasion in northern Syria and enforcing sanctions against Russia.
Such conditions are likely to anger Turkey, which has said the United States had "endless" demands relating to the sale of F-16s and that Washington's behavior wasn't fair.
(Reporting by Humeyra Pamuk; Additional reporting by Patricia Zengerle in Washington; Editing by Doina Chiacu, Don Durfee and Grant McCool)