(Bloomberg) - Fiat SpA (F), the Italian carmaker that controls U.S. auto producer Chrysler Group LLC, will keep Sergio Marchionne as chief executive officer at least three more years to push company growth, Chairman John Elkann said. Marchionne will be responsible for carrying out a new business plan to be presented in May, Elkann said at a briefing at the North American International Auto Show in Detroit. Fiat and Chrysler together offer a good “bench” of eventual successors to the CEO, Elkann said.

The Italian company said on Jan. 1 that it secured full ownership of Auburn Hills, Michigan-based Chrysler in a $4.35 billion deal that will be the biggest in the auto industry since Volkswagen AG agreed to combine with Porsche in 2009. The accord with Chrysler’s other owner was a step in Marchionne’s efforts since taking the helm at Fiat in 2004 to merge the Turin-based company with a competitor to challenge industry leaders Toyota Motor Corp. (7203), General Motors Co. (GM) and VW.

Any successor as CEO “should be an internal one,” Marchionne said at the briefing. Elkann and Marchionne discussed the need for candidates in a conversation yesterday during which they pledged not to repeat the hasty terms of Marchionne’s 2004 appointment, the CEO said.

In May, Elkann named executives such as Richard Tobin, now chief executive officer of Fiat’s truck and tractor affiliate CNH Industrial NV; Lorenzo Sistino, head of CNH’s Iveco trucks unit; Alfredo Altavilla, Fiat’s European chief; Mike Manley, head of the Jeep brand; and Cledorvino Belini, head of Fiat in Brazil, as managers who have been groomed by Marchionne and could eventually run the company.

Fiat rose as much as 1.9 percent and was trading up 0.5 percent at 6.75 euros as of 3:21 p.m. in Milan. The stock has gained 54 percent in the past 12 months, valuing the carmaker at 8.44 billion euros ($11.5 billion).

The merger that Marchionne is seeking for Turin-based Fiat and Chrysler would enable the manufacturers to pool funds and tighten cooperation between the Italian company’s Alfa Romeo, Lancia and Maserati brands and the Chrysler, Dodge and Jeep nameplates. Fiat is open to additional partnerships with other carmakers such as PSA Peugeot Citroen (UG) and Suzuki Motor Corp. (7269), Marchionne said.

Jean-Baptiste Thomas, a spokesman for Paris-based Peugeot, declined to comment.

Marchionne has said he favors a New York listing for the combined entity. Fiat’s board will look at the subject at the end of January during a planned discussion on the company’s structure, and a new listing for the merged manufacturer is technically possible in the second half of this year, he said today, without specifying a location.