David Cameron is to make an EU security plea at Terror Summit.
Britain and France are set to spend £1.5 billion developing the next generation of drones, in a sign of closer co-operation over security and defence.
British Prime Minister David Cameron and French President François Hollande will discuss how they can work together to fight terrorism at a summit in Amiens, France. Cameron is expected to announce more information sharing and greater co-operation between British and French security and police forces.
Cameron will claim the UK is safer as part of the European Union and that membership "gives greater security and greater capacity to project power".
He is due to say: "The UK and France are proud allies. Our meeting here in Amiens is an opportunity to discuss how we can work even more closely together to keep our people safe.
"I am convinced that the UK's membership of the EU gives us greater security and greater capacity to project power globally. In an ever-more uncertain world, we gain from our membership of these international organisations".
Counter-terrorism, the migration crisis, Syria and Libya will be discussed at the summit, the first since the Paris terror attacks.
It will also be attended by Home Secretary Theresa May, Foreign Secretary Philip Hammond and Defence Secretary Michael Fallon.
British Chancellor George Osborne will also be speaking out ahead of the Brexit referendum, making the economic argument for a vote to remain at the British Chambers of Commerce conference.
He is expected to say: "British businesses have access to the largest free trade single market in the world, and many people's jobs and livelihoods in this country depend on that... What is very clear is that British firms cannot have the access they need to the free trade single market without British taxpayers contributing to the EU budget and accepting free movement of EU migrants".