An RT-2PM Topol with two MIRVs may have been tested in 1991, and the missile was tested at least once with four MIRV warheads, but there has apparently been no further development of a multiple warhead version. This became a point of contention during the conclusion of the 1991 START negotiations, at which time the US pressed for a definition of "downloading" (removing warheads from missiles) that would complicate any Soviet attempt suddenly to deploy multiple warheads on the RT-2PM Topol.