Russian President Dmitry Medvedev has said a new arms race could begin in the next decade if Nato and Moscow fail to agree on a joint missile shield.
In his annual speech to the nation, he said he had advocated a "fully fledged joint mechanism of co-operation" at a recent Nato-Russia summit.
On domestic issues, Mr Medvedev argued for families of three children or more to stem Russia's population decline.
Confounding expectations, he did not talk about his own political future.
With less than two years to the next presidential ballot, many believe his powerful predecessor, Vladimir Putin, will seek to return to the Kremlin in his place.
Mr Putin, who was among the audience for the speech, has been serving as prime minister since leaving office in 2008.
Just a few days before the speech, in his video blog, Mr Medvedev warned Russia was in danger of "political stagnation" if it did not create a more level playing field for opposition parties.
Analysts have been wondering if this was a deliberate criticism of the political system largely built by Mr Putin while president. BBC News
