Congress  will be briefed Friday on the arms package, worth an estimated $4.2 billion, said officials who spoke on the condition of anonymity. A formal announcement is expected soon.

"All we've been told is the president has made a decision, and I assume it will be for the F-16 A/B upgrade package," said a senior congressional aide close to the issue.

The president decided against selling Taiwan 66 advanced F-16 C/D model aircraft, despite several requests from Taipei and Congress, the officials said.

The decision ends nearly two years of debate within the administration and Congress over whether to sell advanced strike aircraft.