President Barack Obama on Saturday had what the White House described as an "encouraging" phone conversation with Russian President Dmitry Medvedev, as the two countries sought to work out the remaining issues on a treaty to significantly reduce nuclear arsenals.

Russia and the United States are making "substantial progress" on negotiations for a successor to an expired nuclear weapons treaty, according to a Kremlin statement.

Russia is ready to significantly reduce its nuclear arms, President Dmitry Medvedev said on Saturday ahead of scheduled talks on the topic with US President Barack Obama.

With two major conventional and strategic treaties in limbo for years, Gen Nikolai Makarov presented what appeared to be Moscow's most detailed wish list to date for talks with Washington.