Hundreds of peace activists from across the UK will today try to blockade a nuclear weapons site where warheads for the Trident submarines are made.
Organisations including the Campaign for Nuclear Disarmament are staging the protest at the Atomic Weapons Establishment in Aldermaston, Berkshire.
Demonstrators are planning to sit down or lock themselves together to press home their campaign against the Trident missile system being replaced.
Some Church of England bishops are expected to join the protest.
CND chairman Kate Hudson said: "When all major parties are proposing huge spending cuts, this is the time for ministers to realise that scrapping the Trident replacement would be one very positive and popular cutback. Polls consistently show a clear majority against Trident while, at the same time, a growing number of senior military figures have described the system as 'militarily useless'.
"Presidents Obama and Medvedev are both working towards a nuclear-free world and scrapping Trident would move us towards this goal, improving our security as well as freeing up resources for spending on real priorities, not Cold War relics."