The French presidency says Britain and France are to sign a key deal to ensure their nuclear weapons are safe [EPA]

Britain and France will sign a treaty on Tuesday that will see the two countries test the safety of their nuclear weapons stocks in a joint facility in France.

The French Presidency announced the agreement, which will see a nuclear simulation facility built at Valduc in eastern France, about 45 kilometres northwest of the city of Dijon.

The facility will start operating in 2012, the presidency said, and will enable British and French scientists to model the performances of nuclear materials to ensure the "viability, safety and security in the long term" of their nuclear arsenals.

The unprecedented defence accord, which will also include the creation of a joint military force and sharing of aircraft carriers, will be signed in London by British Prime Minister David Cameron and French President Nicolas Sarkozy.

The Valduc laboratory will work with a French-British research centre based in Aldermaston in southern England. Together the facilities would involve "several dozen" French and British experts and cost both countries several million dollars, the French presidency said.

The Nato allies, western Europe's biggest defence spenders and only nuclear powers, have a centuries-old history of military rivalry and, more recently, have differed sharply over issues such as the Iraq war.

Their new partnership is driven by the desire to maintain cutting-edge military capabilities while at the same time reining in defence spending in the face of big budget deficits.

"Britain and France do share a real interest here ... There are many areas where we can work together and enhance our capabilities and save money at the same time," Cameron told the British parliament on Monday.

Source: Agencies