Bill Couch, a spokesman for the US Naval Sea Systems Command, confirmed that none of the missile tubes delivered by BWX Technologies, one of US contractors, had been fitted into the submarines under construction, according to The Times.
Welding by the company has been suspended until a special probe into the defect is completed, he added.
The newspaper suggested that the defect threatened to hinder the process of replacement of the Royal Navy’s four Vanguard-class ballistic-missile submarines by new Dreadnought-class submarines.
A spokesman for the UK Ministry of Defence, however, said that the nuclear deterrent's modernization program remained on schedule.
"We are aware that a welding quality issue on submarine missile tubes manufactured by US company BWX Technologies is under investigation, but our Dreadnought programme remains on schedule and within budget to deliver the first boat in the early 2030s," the spokesman said, as quoted by the newspaper.
The UK-US cooperation in the sensitive area dates back to the 1962 Nassau Agreement, which paved the way for the launch of the UK Polaris program.