Obama, Medvedev sign nuclear disarmament treaty

US and Russian presidents Barack Obama and Dmitry Medvedev signed a landmark treaty cutting their nations' nuclear arsenals in Prague on Thursday.

Moscow and Washington agreed the treaty after months of tough negotiations bogged down by various disagreements, particularly over US missile defence plans that Russia opposes.

The treaty, which must be approved by the US Senate and the Russian parliament to take effect, is a successor to the 1991 Strategic Arms Reduction Treaty (START), which expired last December.

The so-called "new START" cuts the number of deployed warheads by 30 percent from the levels set in the last major US-Russian disarmament treaty in 2002, specifying limits of 1,550 nuclear warheads for each of the two countries.