This is how you milk more money out of the system in the long run. They do this type of stuff all the time.
The UK will get it's F35's do not worry about that.
Just wait a few years and watch.
Senators today voted to freeze spending on the General Electric/Rolls-Royce F136, the second engine under development for the Lockheed Martin F-35 Joint Strike Fighter (JSF) programme.
The Senate voted to reject an amendment that would have restored more than $600 million to continue development of the F136 and buy the first four production units. Senators also passed another amendment that would block any further spending on the F136 unless Secretary of Defense Robert Gates certifies that the alternate engine programme will both reduce costs and improve the readiness of the F-35 fleet
INDIANAPOLIS --- Rolls-Royce applauds the vote of the US House of Representatives today to continue support for the competitive engine program for the F-35 Joint Strike Fighter (JSF). The House voted 400 to 30 to include $560 million in FY2010 funding to develop and produce the GE Rolls-Royce Fighter Engine Team’s F136 engine