Italian automaker Fiat increased its majority stake in Chrysler on Thursday to 58.5 percent from 53.5 percent, reaching the goal set by the U.S. government after it bailed out and restructured the American automaker in 2009.

Fiat's higher stake in Chrysler comes after the companies' commitment to produce a 40 miles-per-gallon car in the U.S. came to fruition in December. Chrysler said testing by the Environmental Protection Agency on a pre-production version of the 2013 Dodge Dart in late December achieved the 40 mpg rating. On Wednesday, Chrysler issued a commitment to the Department of Treasury to begin production of the Dart.

The acquisition of a further 5 percent of Chrysler is a fundamental step in completion of the integration between our two groups, Fiat and Chrysler CEO Sergio Marchionne, said in a statement.

We have worked hard on achievement of the Ecological Event over the past two and a half years and we are particularly proud of this accomplishment because it represents repayment of the trust placed in Fiat to introduce its fuel-efficient cars and engines to the U.S. market.

Fiat, the Italian owner of brands like Ferrari, originally purchased a 20 percent stake in Chrysler from the U.S. government in July 2009. Fiat's stake increased incrementally as the company and Chrysler met certain goals. This is the fifth time in the past year that Fiat has increased ownership in Chrysler.

A health care trust associated with the United Auto Workers union, the UAW Retiree Medical Benefits Trust, owns the remaining 41.5 percent stake in Chrysler.

The commitment to ecological and sustainable mobility, which has made Fiat the most eco-performing automaker in Europe, is integral to our business strategy, Marchionne said. Together with the know-how developed by Chrysler, we have formed a strong, competitive auto group with a technological capability among the most innovative in the world.

Chrysler is scheduled to introduce the 2013 Dodge Dart next week at the 2012 North American Auto Show in Detroit, reintroducing a brand that was first produced and popularized in the 1960s before it was discontinued. The Dart will be produced at a factory in Belvidere, Ill., the company said.

Chrysler has said it plans to market the Dart by the first half of 2012. It is the first Chrysler vehicle inspired by Fiat's Alfa Romeo Giuletta designs.