nation is the estimated 5 Mt Chinese Dong Feng 5 (DF-5) ICBM (CSS-4) warhead and the Russian UR-100N 5 Mt rocket. US Air Force National Air and Space Intelligence Center estimates that as of June 2017 about 50 R-36M2 launchers were operationally deployed. Elimination In the last decade Russian armed forces have been steadily reducing the number of R-36M missiles in service, withdrawing those that age past their designed operational lifetime. About 40 missiles of the most modern variant R-36M2 (or RS-20V) will remain in service until 2019. As of January 2020, the Strategic Missile Troops had 46 R-36M2s in active service. In March 2006 Russia made an agreement with Ukraine that will regulate cooperation between the two countries on maintaining the R-36M2 missiles. It was reported that the cooperation with Ukraine will allow Russia to extend the service life of the R-36M2 missiles by at least ten to 28 years. According to Interfax report, two R-36M2 missiles are planned to be dismantled by November 30, 2020. The process is to be carried out in accordance with the New START procedures. Design Multiple warheads Missiles of the R-36M family have never been deployed with more than ten warheads, but given their large throw-weight (8.8 tonnes as specified in START), they have the capacity to carry considerably more detonation power. Among the projects that the Soviet Union considered in the mid-1970s was that of a 15A17 missile—a follow-on to the R-36MUTTKh (15A18). The missile would have had an even greater throw-weight—9.5 tonnes—and would be able to carry a very large number of warheads. Five different versions of the missile were considered. Three of these versions would carry regular warheads — yield, yield, or yield. Two modifications were supposed to carry guided warheads ("upravlyaemaya golovnaya chast") — or . However, none of these upgraded models were ever developed. The SALT II Treaty, signed in 1979, prohibited increasing the number of warheads ICBMs could carry. Equally, from a strategic point of view, concentrating so many warheads on silo-based missiles was not seen as desirable, since it would have made a large proportion of the USSR's warheads vulnerable to a counterforce strike. The operational deployment of the R-36M consisted of the R-36MUTTKh, which carried ten 500 kt warheads, and its follow-on, the R-36M2 (15A18M), which carried ten 800 kt warheads (single-warhead versions with either 8.3 Mt or 20 Mt warhead also existed at some