Prime Minister David Cameron said on Friday that Britain and France are working on developing next-generation unmanned drones together as part of their military cooperation, but gave no further details.

Cameron told a news conference with President Nicolas Sarkozy following an annual Franco-British summit that work on building, perhaps, new drones together and in nuclear energy was evidence of what he described as the highest level of bilateral cooperation since World War Two.

Sources told Reuters on Thursday that the two leaders would sign a non-binding letter of intent at the summit on developing unmanned stealth aircraft.

(Reporting by John Irish; writing by Catherine Bremer; editing by Daniel Flynn)