DETROIT — When the two guys who run General Motors, Renault, and Nissan sit down together Friday, they’ll focus on how linking the companies could save money and make them more competitive across the globe.

On the eve of the historic meeting between Carlos Ghosn, the star chief executive of Renault SA and Nissan Motor Corp., and Rick Wagoner, the steady chairman of General Motors Corp., both men said they’ll look at synergies that could be achieved with an alliance of the French, Japanese, and American automakers.

While Messrs. Ghosn and Wagoner will discuss the bigger picture, the real work of crunching numbers to quantify those synergies likely will take until the end of the year, Mr. Ghosn said yesterday in an interview on CNBC.

“How can we quantify what’s at stake? What’s the prize?” Mr. Ghosn asked.

Friday’s meeting, to take place in private at an undisclosed location, could be the start of historic change in the auto industry, with Renault and Nissan taking large stakes in the world’s biggest automaker.

Such an alliance could lead to a struggle for the top job at GM, but Mr. Ghosn said he cannot run another company and keep his present posts.

“I’m not gonna run any other third company. That’s not what is at stake here,” Mr. Ghosn said. “What’s at stake here is building an alliance with a third company and supporting this company if this alliance is signed off.”

Mr. Ghosn sidestepped a question about whether he wanted to run GM.

“I’m saying categorically it’s out of question that I’ll add on top of my two present responsibilities, which is being CEO of Renault and Nissan, another one,” he said.

Mr. Ghosn said during the 45-minute interview on CNBC’s show “Closing Bell” that he and Mr. Wagoner probably will meet one-on-one, with experts from both companies then working on the numbers.

His comments came during a flurry of interviews he gave in New York as he traveled to his meeting with Mr. Wagoner, who also talked to reporters yesterday in Washington.