Pratt & Whitney has won a contract to build 39 engines for a sixth batch of F-35 Joint Strike Fighters, according to Reuters.
The agreement - which Pratt had expected to reach over a month ago - is valued at more than $1 billion.
The Pentagon agreed on the terms of a contract for the sixth and seventh orders of F-35s with Lockheed Martin, which builds the jets, in late July. The government buys the engines separately from Pratt & Whitney, which is the sole producer of engines for the radar-evading warplane.
The negotiations between Pratt and the Pentagon's F-35 program office had focused only on engines for the sixth batch, with separate discussions planned for a seventh batch of F135 engines.
Pratt President Dave Hess had told Reuters in June that he expected to reach a deal with the Pentagon within 30 days on the next engine contract, reflecting a cost reduction of less than 10 percent.
No further details were immediately available about the new agreement in principle, which the sources said was reached by Pratt and government officials last week but which has yet to be announced.
Officials at Pratt and the Pentagon's F-35 program office had no immediate comment on the deal, whose terms will now be finalized in coming weeks and months.
Pratt has said the cost of the F135 engine it builds for the F-35 fighters is down about 40 percent from 2001, when the program began. The company finalized a $1 billion deal for a fifth batch of 35 engines with the Pentagon in May.
The sixth engine contract includes 39 engines - 36 for F-35 planes and three spares, according to Pratt & Whitney.