Mr. Marchionne has been outspoken that the two-tier wage system cannot be sustained in the long term, and suggested that the tentative agreement provided a starting point for the elimination of the tier structure.

“It will go away over time,” Mr. Marchionne said, without providing any further details.

He said that employees at the company, under the tentative agreement, will have a “trajectory of career development,” which implied that lower-paid workers can move up to higher-wage status over some period of time.

Mr. Marchionne also said that cutting health care costs was a key component of the agreement.

The U.A.W. had been discussing creating a health care collective covering workers at all three companies for the purpose of saving money on the costs of medical care and prescription drugs.

“The cooperative arrangement is embedded in the spirit of this agreement, and I really hope it gets implemented,” Mr. Marchionne said.

Mr. Williams said he would present the tentative agreement on Wednesday to union officials from Fiat Chrysler facilities across the country. After that takes place, union members will vote on the pact. He said the vote would probably take place next week.

Despite the absence of details, Mr. Williams and Mr. Marchionne expressed confidence that the tentative agreement would benefit workers as well as the company, which was created after the former Chrysler Corporation went bankrupt in 2009 and needed a government bailout to survive.

Mr. Marchionne said the negotiations were intense in the final hours. “I’m pleased that this thing has come to an end,” he said.