US 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, Reuters reported.

The deal moves ahead with the sale of the modernization package for Turkey's aircraft, after leaders of US 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.