An international group led by Lockheed Martin Corp. received a $3 billion contract yesterday to develop a program that will eventually replace the Patriot missile system.

The new missile system is designed to be wheeled onto the battlefield by soldiers to shoot down jet fighters, drones and some ballistic missiles. Lockheed has been working on the program since 1999, but did not sign the contract to start developing the Medium Extended Air Defense System, known as MEADS, until yesterday.

The Pentagon is developing the system with Germany and Italy, which are contributing 25 percent and 17 percent, respectively, to its cost. The United States is expected to order 48 of the systems, while Germany is expected to buy 25 and Italy 9. France was part of the original program, but dropped out years ago.

The contract was issued by a NATO unit, NATO Medium Extended Air Defense System Organization, which was created to manage the international program.

The Patriot was designed in the 1960s and 1970s to fight the Soviet Union and is too heavy to quickly traverse the battlefield, said Jim Cravens, president of Lockheed's team, known as MEADS International. The Patriot system is also based on proprietary software that cannot be quickly linked with other weapon systems, he said.

The development phase of the program is worth $3 billion. When the company begins manufacturing the system and selling it to other countries the program's value is expected to more than double, Cravens said. "This looks to be a very, very robust program," he said. MEADS will not be operational in the United States until 2014, he said.

The other members of MEADS International are MBDA-Italia, the European Aeronautic Defense and Space Co. and Lenkflugkorpersysteme in Germany.