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The Obama Administration will reportedly delay the release of the U.S.' most ambitious fuel economy proposal ever.

Word is the Department of Transportation (DoT) and the Environmental Protection Agency (EPA) won't be able to string together a Corporate Average Fuel Economy draft for Model Year 2017-25 for public comment by the end of this week, as was initially intended. Instead, sources close to the matter claim the proposal won't be rolled out until November, or possibly even later. But even with the expected delay, the administration should remain on track to meet its deadline of issuing final guidelines by July of 2012.

The National Highway Traffic Safety Administration (NHTSA) and EPA are jointly writing the regulations based on the July agreement, which tentatively calls for automakers to hit a CAFE target of 54.5 miles per gallon by 2025.

Sources claim regulators are moving slower than anticipated on details of the official proposal to ensure it covers issues likely to be voiced during the public comment period.