The declaration, to be signed Thursday, will state that the respective deterrents of both countries remain under national control "but can be co-ordinated, and that there is no extreme threat to Europe that would not prompt a response by both nations," the UK's Ministry of Defence (MoD) and the French presidency said in an overnight statement.

French President Emmanuel Macron will sign the agreement Thursday as he wraps up his three-day state visit to the UK with a bilateral summit, where the allies will "reboot" defence ties with a focus on joint missile development and nuclear co-operation.

France's leader and UK Prime Minister Keir Starmer will co-host the London summit, with the two sides also expected to discuss maintaining support for Ukraine and curbing undocumented cross-Channel immigration.

Ahead of the gathering, which follows two days of varied events spanning pomp and politics, trade and culture, France and Britain announced their "defence relationship" will be "refreshed".

It will see London and Paris order more Storm Shadow cruise missiles -- long-range, air-launched weapons jointly developed by the two countries and called SCALP by the French -- while stepping up work on a replacement system.

The missiles have been shipped to Ukraine in significant numbers in recent years to help Kyiv in its war with Russia.

The new partnerships herald a new "Entente Industrielle" making "defence an engine for growth", said the MoD.

"As close partners and NATO allies, the UK and France have a deep history of defence collaboration and today's agreements take our partnership to the next level," Starmer said in the statement.

Starmer and Macron will also on Thursday dial into a meeting of the so-called "coalition of the willing" on Ukraine, a group of countries backing the embattled nation.