Agreement on development of the new Israeli version of the F-35 will allow Israel to install its own radio and datalink systems, as well as other equipment, on the jets it is buying.

But the deal also covers enhancements to the airplane’s electronic warfare capabilities that will benefit the United States, Israel and the other nine countries that either have already ordered fighter planes, or plan to in coming years.

The radar-evading, multirole F-35 is the Pentagon’s costliest arms purchase, expected to top $396 billion for 2,443 aircraft in three models through the mid-2030s.

Lockheed and its subcontractors are building the stealthy warplane for the U.S. Air Force, Navy and Marine Corps along with Britain and seven other co-development partners -- Italy, Turkey, Canada, Australia, Denmark, Norway and the Netherlands.

In addition to Israel, Japan also has a signed agreement to buy the F-35, which was designed to replace a range of fighter, strike and ground-attack aircraft, including the F-16.

The Defense Department this year postponed production of 179 F-35s until after 2017, stretching development and testing in an effort to curb costly retrofits and save money. The latest restructuring, the third such major revamp, added 33 months and $7.9 billion to the development plan.

Lockheed Martin, the Pentagon’s No. 1 supplier by sales, is developing the F-35 with Northrop Grumman Corp and Britain’s BAE Systems PLC. Britain initially invested $2 billion in the F-35’s development, the most of any of the eight partner nations.

Work on the electronic warfare enhancements will be done largely by BAE Systems, the sources said.