Mario Vazquez Rana, an influential Mexican businessman, was able to resurrect a chain of ailing Mexican newspapers and boost the prestige of the Pan American games as president of the organization. But United Press International, the mammoth wire service that has been hemorrhaging millions of dollars each year, proved to be too much for him.

Friday night, Vazquez Rana threw in the towel and handed control of the company to a former rival, Paul Steinle, who, as president of cable television's Financial News Network, led a bitter battle for control of UPI against Vazquez Rana two years ago.

The agreement does not require Steinle's group to pay Vazquez Rana any cash. It transfers operational control, but not ownership, of the wire service to Steinle's group, said Dwight Geduldig, a spokesman for Steinle. Additionally, Vazquez Rana has set up lines of credit to cover potential liabilities and operating costs for the wire service, which reportedly has been losing $1 million to $2 million a month.

Steinle, who will be the new president of UPI with control of day-to-day management, plans to keep the current UPI management but has not yet drawn up a business plan. No decision has been made on whether to lay off employees or to launch new ventures, Geduldig said.

Steinle and Earl Brian, chairman of FNN, the New York-based cable network specializing in business information and stock market quotes, have formed a new company to run UPI. The company is called WNW Group Inc.; WNW stands for World Newswire. Brian will raise money and handle financial operations.

It was the latest in a roller-coaster existence for UPI, which has been struggling for years to find a formula for profitability. In the past decade, UPI has endured three owners, a Chapter 11 bankruptcy filing, constant management turmoil and labor disputes.

When Vazquez Rana paid $41 million to acquire UPI in June 1986, rescuing it from bankruptcy protection, he vowed to restore the wire service's prestige. But by early last fall, after a tumultuous year and losses that reportedly reached $1 million to $2 million a month, Vazquez Rana approached Steinle and Brian about buying the company, Geduldig said.

Steinle and Brian, who offered $40 million for the wire service two years ago, were more wary this time. They sent an auditing team to UPI in September to examine financial records. After months of examination, the auditors found the finances "murky," Geduldig said. "There were transactions that had taken place in which there was not proper documentation, from an auditor's standpoint," he said. There also were numerous lawsuits pending against UPI.

Geduldig said Steinle and Brian did not want to buy the company because of the financial entanglements. "Vazquez Rana then said, 'I do not want to run this company anymore. How about taking over operational control?'" Geduldig said.

Officials of the Wire Service Guild, which represents UPI employees, have speculated that the agreement might have been structured to get around a stipulation giving employees first right of refusal on any sale.

Steinle and Brian agreed to take operational control after Vazquez Rana said he would establish lines of credit to cover potential liabilities and operating costs. The final agreement was reached at 6 p.m. Friday, Geduldig said.

Vazquez Rana has turned over his stock voting rights, for which WNW paid no cash, to WNW for a minimum of 10 years, Geduldig said.

In a statement released by UPI, Vazquez Rana said that he was getting "present and future financial considerations totaling more than $55 million." Geduldig declined to elaborate, saying that Vazquez Rana had requested that the details be kept private.

Because Vazquez Rana wanted to keep the negotiations confidential, Steinle and Brian were unable to interview UPI managers and thus have not developed a business plan, Geduldig said. He said that Steinle was at UPI headquarters in Washington yesterday to begin putting together a strategy for reviving the company.

When Steinle attempted to buy UPI in 1986, his business strategy for UPI included joint ventures with FNN and Data Broadcasting Corp., a Vienna company that provides electronic news summaries. The strategy also included establishing a new business division to develop more retail news, data and information products.

FNN and Data Broadcasting Corp. are owned by Infotechnology Inc., a New York-based company that sells electronic data news, an area that Steinle is expected to explore with UPI. Infotech owns, or has controlling interest in, 15 companies, including Hadron Inc., a Fairfax-based professional services and telecommunications company. Steinle was the president of Data Broadcasting Corp. until he resigned recently to become UPI's president.

Steinle called officials of the Wire Service Guild late Friday to inform them of the change and to invite them to meet with him Monday afternoon in Washington. Dan Carmichael, secretary treasurer of the Guild, declined to comment on the transaction until members had a chance to talk to Steinle.

"The union's position has been firm and clear all along -- that we support an integrated full-service news company that can guarantee the integrity of its news product," Carmichael said.

Carmichael said the Guild's position is that an agreement between Vazquez Rana and the Guild during the bankruptcy proceedings gives the employees the right of first refusal is a sale should take place. Geduldig agreed, saying that if the company should become profitable in the future, "the employees will still have the first right of refusal to buy the company."