A research project into nuclear fusion will continue to receive funding from the UK, if the European Union agrees to keep it in Oxfordshire.
The Joint European Torus (Jet) in Culham is home to the world’s largest fusion reactor.
The EU covers 88% of the running costs, but the UK’s contract to host Jet ends in December 2018.
The UK government has committed to paying its “fair share” of the project if the EU extends the contract to 2020.
The EU currently provides £60m towards Jet and the government said a discussion on an “appropriate funding split” would take place after any contract extension.
Science Minister, Jo Johnson said: “Our exit from the EU has not altered our desire and willingness for the UK to continue playing a leading role in furthering our scientific understanding.
“Today’s announcement aims to provide the necessary reassurance for us to continue this partnership.”
Professor Ian Chapman, chief executive officer of the UK Atomic Energy Authority, which manages Jet, said the authority was “pleased” with the government’s commitment.