UK and France agree to joint nuclear weapons tests
The plans will see one centre set up in the UK to develop technology and another in France to carry out testing.
Prime Minister David Cameron and President Nicolas Sarkozy will also outline plans, at a London summit, for a joint army expeditionary force.
Downing Street called the measures "practical", but Labour said they left "big questions" over the UK's defences.
A Downing Street spokesman said: "This summit marks a deepening of the UK-France bilateral relationship. Ours is now a strategic partnership tackling together the biggest challenges facing our two countries."
The summit comes two weeks after the UK government announced cuts to its armed forces, in the first strategic defence review since 1998, as part of savings aimed at reducing the country's budget deficit.
Under the plans, £750m will be saved over four years on the Trident nuclear missile system by cutting the number of warheads.
Harrier jump jets, the Navy's flagship HMS Ark Royal and planned Nimrod spy planes will also be axed, but two new aircraft carriers were spared.
Mr Cameron and Mr Sarkozy are to sign two treaties - one on greater general military co-operation and the other on nuclear weapons; Kazinform cites BBC News. See www.bbc.co.uk for full version.