ILS currently uses only Proton rockets while Atlas rockets are operated by United Launch Alliance, a partnership between Lockheed Martin and Boeing.

The shares were purchased from Space Transport, based in the British Virgin Islands. With this deal, the marketing arm becomes a part of the manufacturing body. However, financial terms have not been disclosed.

The transaction puts all of ILS in Russian hands, with Moscow-based SP Korolev Rocket and Space Corp Energia, a semiautonomous company, owning a 17 percent stake.  Post acquisition, ILS will remain an American company at its present location in Delaware.

Some experts are of the opinion that Khrunichev has become increasingly focused on work for the Russian military in recent years and that the move to take control of ILS could be a way of pulling back from the commercial market.

Space Transport bought Lockheed Martin's 51 per cent stake in ILS in 2006. Space Transport was created in 2006 with the sole purpose of holding an interest in ILS, and its chairman is Mario Lemme, a longtime adviser to ILS who served on the company's board for three years. He has also invested in several other businesses in Russia.

"Building on our strong working relationship with the ILS team, this transaction will cement ILS's leadership role in the commercial launch services industry," said Vladimir Nesterov, general director of Khrunichev.

Frank McKenna, ILS president, said, "We have an outstanding relationship with Khrunichev delivering commercial Proton launch services for our customers over the past 15 years. For ILS employees and customers, there will be no change in operations or management and we will continue our focus on performance. The completion of this transaction only strengthens the relationship with our launch partner, Khrunichev."

Khrunichev, named after Soviet minister Mikhail Khrunichev and based in Moscow, produces the Proton rocket, which is launched from the Baikonur Cosmodrome in Kazakhstan, and is developing another rocket, the Angara. Khrunichev includes among its branches a number of key manufacturers of launch vehicle and spacecraft components in Moscow and in other cities of the Russian Federation.

Khrunichev was transferred to the Salyut Design Bureau in the late seventies, and then between 1981 and 1988 was part of NPO Energia. It became an independent entity in 1988. It was also the manufacturer of manned space stations including Mir, the Salyut series and the Almaz modules.

ILS holds the exclusive rights worldwide to market and sell the services of the Proton and Angara. It provides satellite customers with a complete array of services and support, from contract signing through mission management and on-orbit delivery. ILS is a US company incorporated in Delaware, and headquartered in McLean, a suburb of Washington, DC.

ILS competes with launch companies such as France's Arianespace, India's Antrix and Sea Launch, a Long Beach, California, joint venture between US's Boeing and a Ukrainian rocket company.

Some key ILS statistics:

• Backlog of 22 orders totaling nearly $2 billion
•  45 ILS commercial Proton missions flown since 1996
• Only launch provider with two commercial launch pads
• Approximately 60 employees, based in McLean, Virginia.