The United States is planning to station nuclear weapons in the UK for the first time in 15 years, according to reports.
Procurement contracts reportedly confirm that the weapons will be three times the strength of the Hiroshima Bomb.
The US removed nuclear missiles from the UK in 2008 after judging the Cold War threat from Moscow had diminished.
The news comes in the wake of warnings that Nato countries need to ready their citizens for war with Russia.
Admiral Rob Bauer, a senior Nato military official, warned last week that private citizens should prepare for all-out war with Russia in the next 20 years.
General Sir Patrick Sanders, the head of the British Army, even went as far as to warn the public would need to be called up to fight if there was war with Russia because the Army was too small.
His comments forced No 10 to rule out conscription.
"The British military has a proud tradition of being a voluntary force. There are no plans to change that," Rishi Sunak's spokesman said.
The return of American weapons to the UK is part of a Nato-wide programme to develop and upgrade nuclear sites in response to heightened tensions with the Kremlin since the invasion of Ukraine in February 2022.
Russia has previously stated that the placement of US weapons in Britain was to be viewed as an "escalation" and would be met with "compensating counter-measures".
Unredacted documents on the United States Department of Defence's procurement database reveal plans for a "nuclear mission" that would take place "imminently" in RAF Lakenheath - where nuclear weapons were stored during the Cold War.
The Pentagon refused to comment on speculation that a new "surety dormitory" was intended for the base.