After ending its hybrid partnership with Toyota, Nissan is hard at work on a system of its own.

Nissan unveiled an all-new Altima range at last week's New York International Auto Show, but a hybrid variant was conspicuously absent. We now know why.

Nissan decided a while ago that it wanted to develop its own hybrid system, which is why it ended its deal with Toyota that saw a short-lived and generally unsuccessful Altima Hybrid that used Toyota's Synergy Drive system. Now, already two years behind its original schedule, USA Today confirms that Nissan is aiming to add a hybrid option for the new Altima in two more years.

Two years is a virtual eternity in the auto industry, especially considering the competitive nature of the midsize sedan segment, where Ford and Toyota have been vying for class-leading fuel economy.

Plenty of rumors surround the Altima Hybrid's powertrain, but few facts are known at this point. A plug-in system is a likely option, while early reports have suggested that a supercharger could provide additional propulsion.