US President Barack Obama and his Russian counterpart Dmitry Medvedev are close to finalizing the most comprehensive nuclear arms control treaty in two decades, dpa quoted US and Russian media as reporting. The new Strategic Arms Reduction Treaty (START) would require both countries to reduce their arsenals of long-range nuclear weapons to between 1,500 and 1,675 missiles each. The new treaty replaces a 1991 agreement that expired in December. There would also be cuts to warheads and bombs based on planes, ships and land. The Kremlin announced a breakthrough late Wednesday, reported the Washington Post in its Thursday edition. "All documents related to the new treaty have been agreed upon," said a Kremlin spokesman, speaking anonymously, reported the paper. The paper further reported that White House officials were less forthcoming, with White House spokesman Robert Gibbs telling reporters that Obama and Medvedev were "close" to an agreement, but needed to speak by phone before any announcements could be made. There have been reports that there could be a signing ceremony for the new treaty in Prague in April. Some analysts have said this would be the most significant arms control agreement between the two countries, since the 1993 signing of the START II treaty, which was never ratified by Russia. Before the treaty can come into effect, it must be ratified by parliaments in both countries, a step that is not guaranteed.