Updated 12:20 p.m. EST

PARIS — Satellite and rocket builder Orbital Sciences Corp. on Dec. 16 confirmed that it has contracted with Russia’s Energomash to provide RD-181 engines to power the first stage of Orbital’s Antares rocket, replacing the AJ-26 engine, also from Russia, that Orbital suspects was the origin of Antares’ Oct. 28 failure.

Dulles, Virginia-based Orbital had withheld public announcement of the engine until Dec. 16 despite widespread reports in Russia of the selection, saying it did not want to show its hand in advance of one or more U.S. rocket-selection competitions.

Orbital announced its choice via Twitter and through an article in Aviation Week and Space Technology.

We can confirm the @AviationWeek article http://t.co/DqVnqfZ0nC RD-181 engine meets schedule and technical requirements. No other options do — Orbital Sciences (@OrbitalSciences) December 16, 2014

Khimki, Russia-based Energomash also supplies the RD-180 engine to United Launch Alliance of Denver for U.S. government launches of ULA’s Atlas 5 rocket. The ULA contract with Energomash is handled through RD Amross of Cocoa Beach, Florida, whose contract terms are now under review in the U.S. Congress.

Orbital apparently will contract directly with Energomash. Russia’s Izvestia press agency on Dec. 17 quoted an official from the Russian space agency, Roscosmos, as saying the Energomash-Orbital deal is valued at about $1 billion and includes a firm order for 20 engines, plus two options for 20 engines each.

Orbital spokesman Barron Beneski said in a Dec. 17 statement:

“Our order with Energomash can take us through 2020, with firm orders that will allow us to fulfill our CRS commitments for NASA and several more options that can be exercised along the way as needed. Naturally, we are not discussing price.”

Beneski said the $1 billion contract value being quoted in Moscow is incorrect.

“If all the options under the contract were exercised, the total value would be significantly less than $1 billion,” Beneski added in an email to SpaceNews. “I can’t be more precise than that.”

Despite the widely assumed choice of a Russian engine and the announcements in Russia, Orbital’s choice maintained an element of surprise because of the political context. U.S.-Russian relations have soured since early this year and Russia’s annexation of Ukraine’s Crimea and continued implication in eastern Ukraine.

The United States and the European Union have slapped multiple sanctions on Russian businesses without touching the ULA-RD Amross-Energomash contract directly. But the U.S. Congress has moved to limit long-term reliance on Russian engines.

Orbital is planning to merge with the aerospace and defense division of ATK or Arlington, Virginia. The merger was delayed as ATK evaluated the consequences to Orbital of the Oct. 28 Antares failure, and is now subject to shareholder votes by both companies scheduled for Jan. 27.

ATK officials said they conducted their own due-diligence review of Orbital’s Antares post-failure business prospects, including an assessment of political risk – presumably associated with the Russian engine selection – and concluded that the merger should continue.

In its Twitter statement, Orbital said it would take delivery of the first RD-181 engines in 2015, with a launch scheduled for 2016.

First deliveries of the newly-built #RD181 engines in mid-2015 to be ready for next #Antares flight in early 2016. — Orbital Sciences (@OrbitalSciences) December 16, 2014

The Izvestia report cited the Roscosmos official as saying the Orbital-Energomash contract excludes launches of defense payloads. Orbital has said that beyond its initial contract with NASA to supply Antares launches of cargo to the international space station, it is looking for commercial and other U.S. government business.