Orbital Sciences Corporation has sued ULA seeking damages of between $515 million to $1.5 billion for blocking sales of the Russian-built RD-180 that Orbital wants to use in its Antares launch vehicle, Space News reports.

Orbital of Dulles, Va., claims Denver-based ULA has not only illegally prevented open-market sale of the RD-180, but also has monopolized the launch-services market for certain satellites in violation of U.S. antitrust laws, according to a complaint filed June 20 with the U.S. District Court for the Eastern District of Virginia in Alexandria.

Orbital wants a federal judge to strike down an exclusivity agreement ULA has with its engine supplier, RD AMROSS, and to force ULA to pay Orbital at least $515 million — and potentially more than $1.5 billion — for damages arising from ULA’s alleged monopolization of “launch systems and services used for medium-class payload missions,” according to court papers. Orbital wants the case to go before a jury.

The suit marks an escalation in Orbital’s spat with ULA over the Russian-made RD-180 engine, which is imported to the United States. by a company called RD AMROSS, a joint venture of United Technologies Corp. of Hartford, Conn., and NPO Energomash of Moscow, which manufactures the engine. United Technologies Corp.’s recently divested rocket propulsion division is the original U.S. partner in RD AMROSS, but the joint venture has not yet conveyed as part of that transaction….

Because of an exclusivity agreement forged decades ago with Lockheed Martin, one of ULA’s two parent companies along with Boeing Co., RD AMROSS is only permitted to sell the RD-180 to ULA. Lockheed Martin, which needed a main engine for its new line of Atlas rockets, helped fund the RD-180’s development.