Two American defence officials seemingly jumped the gun by disclosing details of Trident renewal - which will be supported by US technology – in committee hearings earlier this month, it has emerged.
Strategic Command Admiral Charles Richard told a Senate hearing last week that a replacement warhead called W93 or Mk7 was needed in the US.
He added: “This effort will also support a parallel replacement warhead programme in the United Kingdom whose nuclear deterrent plays an absolutely vital role in Nato’s overall defence posture.”
The Ministry of Defence (MoD) has confirmed it is working towards replacing the warheads after testimony surfaced.
It is understood the UK government has been unable to find the time to inform parliament, which is in recess, but an official announcement will be made when MPs return to Westminster.
Mr Richard is not the only US official to have spoken about the agreement before the UK government publicly confirmed it.
Alan Shaffer, the Pentagon’s deputy undersecretary of defence for acquisition and sustainment, reportedly told a conference earlier this month: “I think it’s wonderful that the UK is working on a new warhead at the same time, and I think we will have discussions and be able to share technologies.”
His comments were reported by trade publication Defense Daily.
A Ministry of Defence spokesperson, said: “As previously stated in the 2015 defence review, we can confirm that we are working towards replacing the warhead.
“We have a strong defence relationship with the US and will continue to remain compatible with the US Trident missile.
“An announcement about the UK’s Replacement Warhead Programme will be made in due course.”
An MoD’s update to parliament published shortly before Christmas did not confirm the upgrade.
“Work also continues to develop the evidence to support a government decision when replacing the warhead,” it said at the time.
Boris Johnson has long backed the proposed replacement and the Conservatives committed to renewing the deterrent ahead of the election.
The cost has been estimated at £31bn.