The UK and France are to sign a treaty agreeing to the joint¹ development and testing of nuclear warheads.

英国与法国将要签署一项共同开发、试验核弹头的协议。

The two leaders will announce plans for French planes to use British refuelling aircraft

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（远征军） .

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 bilateral²（双边的） relationship. Ours is now a strategic partnership³ 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 savings⁴ aimed at reducing the country's budget deficit⁵.

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.

Operational veto

The latter will establish a centre in the UK to develop technology and another one in France to carry out the testing.

It is understood that each country will still control its own warheads, and that nuclear secrets will not be shared.

The other treaty will allow the setting up of a "combined joint expeditionary force", thought to involve a brigade（队列） of about 5,000 soldiers from each side.

Each country will retain a veto（否决，禁止） for each operation, which will operate under one military commander to be chosen at the time.

The UK and France have also agreed to keep at least one aircraft carrier at sea between them at any one time.

Each will be able to use the other's carrier in some form, certainly for training and possibly operations.

Meanwhile, France is to use British A400M fuelling aircraft when there is spare capacity, with plans in place for common maintenance and training.