In the memo, sent 4 June, acting Secretary of the US Navy Thomas Harker said the navy would have to choose one programme to pursue, with the other two postponed for later years.

Harker wrote: “The Navy cannot afford to simultaneously develop the next generation of air, surface and subsurface platforms and must prioritise these programmes balancing the cost of developing next-generation capabilities against maintaining current capabilities.

“As part of the POM 23 [programme objective memorandum 2023] budget, the Navy should prioritise one of the following capabilities and re-phase the other two after an assessment of operational, financial and technical risk.”

The US Navy had previously stood up a programme office to develop a replacement for the F/A-18E/F Super Hornet and this month established another office to pursue the development of a new guided-missile destroyer.

The mulled future destroyer would replace the long in-service Arleigh Burke-class of destroyers. Plans for a future submarine the SSN(X) would form the replacement for the Virginia-class submarine.

USNI News reported that all three programmes are at similar stages of development and all three are expected to deliver results before the end of the current decade.

In its Fiscal Year 2022 budget request, the US Navy has earmarked $121.8m for the development of the new destroyer dubbed DDG(X). In the same period, the Navy is set to invest $98m in efforts to design and develop the SSN(X).

The US Navy has not said how much it will invest in NGAD development in 2022.