Stellantis, the carmaker forged from the merger of Fiat Chrylser and Peugeot-owner PSA, is "very confident" of delivering its planned 5 billion euros ($6.1 billion) of synergies, including 80% within four years, its new chief executive said on Tuesday.

Carlos Tavares's comments came as Stellantis' shares surged 10% on their New York debut, mirroring strong increases in its French and Italian listed stock since their launches on Monday.

In his first press conference as Stellantis CEO, Tavares also said he had created a task force to find out "what went wrong" for both Fiat Chrysler (FCA) and PSA in China.

The merger, completed on Saturday, has created the world's fourth-biggest carmaker to help make the switch to the new era of electrification.

"The purpose is not to be big, but to be great at what we do," Tavares said.

Both PSA and FCA fared poorly in China, the world's largest car market. Tavares said the task force, consisting of Stellantis' top five executives, would work on solutions for a come-back there.

When asked if options could include finding a new local partner, Tavares said the company "would not exclude anything."

Stellantis will have 14 brands, from FCA's Fiat, Maserati and US-focused Jeep, Dodge and Ram to PSA's traditionally Europe-focused Peugeot, Citroen, Opel and DS.

Tavares, who was previously PSA's CEO, said all 14 brands would be given a chance "to rebound" and invest in new products as the group focuses on profitable growth.

Stellantis will launch 10 new electrified vehicle models in 2021, he added.