The US Department of Defense announced Tuesday approval to sell new KC-46 Pegasus aerial refuelling aircraft to its staunch Middle East ally Israel.

Israel would buy up to eight of the Boeing-built aircraft and related equipment for an estimated $2.4 billion, the Pentagon's Defense Security Cooperation Agency said after the State Department approved the proposed deal, of which Congress has been notified.

The multi-role aircraft makes mid-air refueling possible for fighter jets and other aircraft, but can also be used for military transport.

"The United States is committed to the security of Israel, and it is vital to US national interests to assist Israel to develop and maintain a strong and ready self-defense capability," the Defense Security Cooperation Agency said in a statement.

It said that Israel's having its own KC-46s would help back up the US military's own, "potentially freeing US assets for use elsewhere during times of war."

The proposed sale comes despite delays in the Pegasus program

The main question is about the design of its refueling function. The US Air Force has found significant problems with the KC-46's remote vision system, essential in trying to line up and attach the refueling boom to the aircraft seeking to fill up its tanks.

Air Force Chief of Staff General David Goldfein said they were pressing Boeing to address the problem.

"Right now we are in final negotiations with the company on the fix," he told the Senate Armed Services Committee on Tuesday.

The first KC-46 was delivered to the US Air Force a year ago and the service has ordered 179 of the planes.

Israel is the second country to be approved for the KC-46.

Boeing is building two of the aircraft for Japan.

Based on the airframe of the Boeing 767, the KC-46 is to replace the Air Force's aging line of KC-10 and KC-135 tankers, many of which were manufactured during the Cold War.afp