Senior Canadian government officials say Canada will under no circumstances be purchasing F-35s on an expedited basis and that no decision has been made on which new warplane to buy.

In the face of a U.S. military report that Ottawa has made a secret decision to buy U.S. F-35 stealth fighters, officials say the lack of firm details on cost and capabilities has not instilled confidence. They say Lockheed Martin has not provided Canada with enough basic information to justify acquiring the overbudget F-35s, which constitute the most expensive military procurement program in U.S. history. The fact that glitches prevented Lockheed Martin from flying the F-35 at this summer's Farnborough airshow in Britain only increases caution in Ottawa, a senior Canadian official said.

"What we have seen is that there have been lots of reports and studies provided. And as a result we now know everything there is to know except the cost and capabilities, which are key for an investment of this nature," the source said.

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A leaked, classified, high-level Pentagon briefing – dated Oct. 27 – by the top U.S. Air Force general heading the F-35 program, to the secretary of the Air Force, said that Ottawa wants four F-35s next year and that the Harper government must deliver a signed "letter of intent" by "mid-November" to secure the deal.

If Canada made good on the signed letter of intent, four F-35s, currently being produced to specifications for the U.S. Air Force, would be delivered to the Royal Canadian Air Force in 2015. Canada would then "payback with LRIP 9 aircraft," which means Low-Rate Initial Production, two years later, according to the Pentagon document.

The Pentagon confirmed last week that the leaked briefing slides were authentic. Canada's pitch for early delivery of four F-35s was laid out in detail on slide 11 of a 14-slide, high-level briefing to Deborah Lee James, secretary of the Air Force, by Lieutenant-General Christopher Bogdan, the F-35 program executive officer.

Locking in early delivery for four F-35s would allow Canada's fighter pilots – who covet the "fifth-generation" strike fighter – to gain experience with its sophisticated (and troubled) helmet-mounted sensors while awaiting delivery of dozens of the single-engined strike fighter.

Plagued by cost-overruns and delays, the Lockheed Martin F-35 Lightning II Joint Strike Fighter, as it is officially known, suffered its most embarrassing setback last summer when one of the warplanes caught fire even before taking off. That led to the grounding of all F-35s and scrapped what was supposed to be a high-profile display of its capability at the air show in Britain.

With a report from Paul Koring in Washington