Fiat and Chrysler Chief Executive Sergio Marchionne said he had no immediate plans to merge the two automakers as shares in a new stripped-down Fiat began trading Monday.

"I have no plans to merge Fiat and Chrysler today," Marchionne told journalists at a ceremony organized at the Milan stock exchange for the first listing of spin-off Fiat Industrial, which contains the conglomerate's non-automotive elements.

"I think we have done a relatively decent job in the last 18 months" in terms of "industrial integration," he said, adding "a legal merger is not going to change our lives."

Fiat owns 20 percent of Chrysler, which it took operational control of in June 2009 after the US automaker nearly went bankrupt.

But Marchionne said it was "possible" Fiat may boost the holding to 51 percent "if Chrysler decides to go to the market in 2011."

In September 2010 Fiat shareholders approved the Italian auto giant's plan to separate its car and non-car making activities as part of a drive to increase its global clout.

The spin-off, which took effect on Jan. 1, leaves a car-only Fiat with its own brand plus Ferrari, Lancia, Alfa Romeo, Maserati and its components and motor activities.

Its truck making and agricultural and construction machine makers became part of the new Fiat Industrial.