HMS Queen Elizabeth could replace HMS Prince of Wales after breaking down off the South coast

Although a decision has not yet been made, HMS Queen Elizabeth could be soon heading to the US coast. Credit: PO Jenkins/MoD Crown Copyright/PA

Royal Navy flagship HMS Queen Elizabeth is likely to stand in for its sister ship during diplomatic visits and military exercises off the US coast after the HMS Prince of Wales broke down off the Isle of Wight.

The warship left from Portsmouth Naval Base on Saturday (27 August) before an "emerging mechanical issue" occurred while off the south-east coast of the Isle of Wight.

The departure of the Nato flagship had already been delayed from Friday (26 August) because of a technical problem, but a decision was taken to sail anyway.

Shortly after the 65,000-tonne ship sailed, a mechanical fault was discovered with the starboard shaft.

The vessel's departure had earlier been delayed from Friday, August 26, because of a technical issue. Credit: Ministry of Defence

Navy divers have been inspecting the ship and found that a coupling on the propeller shaft had failed.

HMS Prince of Wales is expected to return to berth at Portsmouth Naval Base to unload crew and equipment before heading to dry dock for repairs, probably at Rosyth in Scotland where it was built.

The navy had said prior to the departure of HMS Prince of Wales that notable port stops during the three-month deployment would be in New York, Halifax in .Canada and the Caribbean.

It is understood that the crew of sister ship HMS Queen Elizabeth have been warned they may be sailing to the USA, altering its current plans for deployments to the Baltic and Mediterranean, although a decision has not yet been made.

Festival goers at the Victorious Festival gave the carrier a colourful send-off on Saturday afternoon. Credit: Ben Mitchell/PA

A Royal Navy spokesman said: "Diving inspections on HMS Prince of Wales' starboard shaft have shown that a shaft coupling has failed.

"We are looking at the best way to carry out what will be a complex repair and assessing options for the delivery of Royal Navy outputs against current priorities and future commitments and will update in due course."