The Financial Times posted Saturday night that the discussions were at an “advanced” stage and could lead to “extensive cooperation”.
The Wall Street Journal said the talks were “wide-ranging” and could include Renault and Fiat Chrysler “joining large portions of their businesses”.
However, The New York Times said the discussions were in early stages, the specifics unclear and “could still collapse”.
Contacted by AFP, neither Renault nor Fiat would comment.
The Financial Times, quoting multiple people informed on the talks, said: “The agreement may ultimately lead the carmaker (Fiat-Chrysler) to join the Renault-Nissan-Mitsubishi Alliance in the future,” if Nissan could be won over.
Such an automaker alliance would become the world’s biggest, a title Renault-Nissan-Mitsubishi currently vies for with Germany’s Volkswagen.
Renault holds 43% of Nissan which in turn owns 15% of its French partner Renault.
The imbalance causes frictions in a relationship that has been tested by the arrest of former Renault and Nissan chief Carlos Ghosn in Tokyo.
He was bailed for a second time on April, 25 and is now preparing for trial on four charges of financial misconduct ranging from concealing part of his salary to using Nissan funds for personal expenses.
The reports did not spell out the level of any involvement by Nissan in the current discussions, although one FT source said it was absent.
Early this year rumours circulated that Renault was interested in Fiat-Chrysler after its hopes for a merger with Nissan or even French competitor PSA faded.