The RD-180 is a rocket engine designed and built in Russia. It features a dual combustion chamber, dual-nozzle design and is fueled by a kerosene/LOX mixture. Currently, RD-180 engines are used for the first stage of the US Atlas V launch vehicle.
The RD-180 is derived from the RD-170/RD-171 line of rocket engines, which were used in the Soviet Energia launch vehicle, and are still in use in the Russian/Ukrainian Zenit launch vehicles. The roots of the RD-180 rocket engine extend back into the Soviet Energia launch vehicle project. The RD-170, a four-chamber engine, was developed for use on the strap-on boosters for this vehicle, which ultimately was used to lift the Buran orbiter.
After the collapse of the Soviet Union President George H.W. Bush did not want USSR rocket expertise, especially the nuke-tipped ICBM kind to other countries. President Bush and then President Clinton urged U.S. aerospace executives to look for Russian rocket business partnerships that made sense.
Russia’s state-controlled NPO Energomash has contracts worth over $2 billion dollars to supply two major U.S. aerospace companies, United Launch Alliance (ULA) and Orbital ATK, with rocket engines. The RD-180 has flown 50 times on U.S. missions with 100 percent success.
In September 2014, ULA announced that it has entered into a partnership with Blue Origin to develop the BE-4 LOX/methane engine to replace the RD-180 on a new first-stage booster that would succeed the Atlas V. The BE-4 Blue Origin engine will fly no earlier than 2019.
Russia is now stable. Any sale or proliferation of Russia Space and rocket technology will be because Putin approved it.
The US no longer has the strategic need to pay Russia and cost savings is not a justification to provide money for Russian Rockets. If it was just costs and competitive bidding then why not also include launch bids from China as well ? Because United Launch does not have a contract for Chinese rockets.