Britain is prepared to give some of its territory in Cyprus to the island's Greeks and Turks as part of a peace deal.
The plan has provoked opposition
The UK Government has offered 45 square miles (115 square km) - half of its total territory in Cyprus - as part of a United Nations settlement.
Britain has 98 square miles on the south coast of the island in the form of two sovereign military bases, housing 3,500 troops.
The Foreign Office said the area being offered was mostly farmland and would not alter military effectiveness.
UN Secretary General Kofi Annan is touring the region in the hope of clinching a last-minute agreement between the Greek Cypriot and Turkish Cypriot leaders.
The area has no military infrastructure and therefore this would have no adverse impact on the function or operational capability of British forces
Foreign Office spokeswoman
Both sides have until 28 February to agree to the latest UN power-sharing package of proposals.
A UK Foreign Office spokeswoman told BBC News Online the UK had agreed to cede 45 square miles as part
of the latest revision to the UN settlement process.
"The European Council in Copenhagen decided the issue of territorial reassignment was a key issue to leading to agreement to the settlement," she said.
"So the British Government gave urgent consideration to whether it could bridge the gap and these areas were identified."
"The areas being offered have no military significance and are mostly farmland.
The United Nations deadline is 28 February
"There is no military infrastructure and therefore this would have no adverse impact on the function or operational capability of British forces."
She added the deal became invalid if rejected by either side or in a referendum.
Akrotiri is the largest RAF base outside
the UK and is expected to play a significant role in any military action against Iraq.
The UK retained sovereignty over the territories when it granted the east Mediterranean island independence in 1960.
Cyprus is due to sign a formal treaty to join the European Union in two months' time, but without a deal, the Turkish part of the island will in effect be left out of the EU.