The U.S. Navy is set to order 33 fewer Lockheed Martin Corp F-35 fighter jets than originally planned over the five years starting in fiscal 2015 due to budgetary pressures, a defense official said.

In a move that will sharply slow work on the F-35 model built to land on aircraft carriers, the Navy will ask Congress to fund 36 F-35Cs instead of 69, said the official, who could not speak publicly ahead of Tuesday's release of the 2015 budget request.The Air Force is also deferring orders for four conventional landing F-35 A-models in fiscal 2015, but is expected to resume its planned orders for the jet in 2016 and beyond, said a second source familiar with the plans. It plans to order 238 in total.

The Marine Corps, which expects to start using its F-35 B-model jets in combat from mid-2015, is sticking to its projected orders of 69 jets for the period, the sources said.That adds up to 343 F-35s to be funded by the U.S. military through fiscal 2019, excluding three Marine Corps jets that could be added to the Pentagon's war funding request, which will be submitted in April or May.