(The New York Times)- - In a sign of the increasing firepower of private equity, Kohlberg Kravis Roberts & Company secretly made a $50 billion bid last month for Vivendi, the French entertainment and telecommunications company, according to people involved in the talks.

The takeover bid marks the largest leveraged buyout offer in history and demonstrates the growing prowess of private equity on the global stage.

Negotiations between Kohlberg Kravis and Vivendi, which reached a fevered pitch late last month after taking place in fits and starts, appear to have stalled if not collapsed entirely, people involved in the talks said. Still, one person involved in the talks suggested that it remained possible the talks could resume.

Another person involved in the discussions, however, called Kohlberg Kravis’s bid “just an opening salvo” and described the negotiations as “dead and not coming back.”

Whatever the case, the negotiations represent the latest example of private equity’s ability to take aim at some of the world’s largest companies, once considered unthinkable prey.

Flush with some $2 trillion in buying power, private equity is now focusing its attention on blue-chip firms and setting records for bigger and bigger takeovers.

In the last year, Kohlberg Kravis led a consortium of investors to acquire HCA for $33 billion, eclipsing the record that it had held for its takeover of RJR Nabisco in 1989, a deal that came to define an era when it was chronicled in the book “Barbarians at the Gate.”

Other deals, like the $15 billion purchase of the gas pipeline company Kinder Morgan or the sale of Freescale Semiconductor for $17.6 billion to a group of private equity firms led by the Blackstone Group, have redefined the size and scope of leveraged buyouts, once called “boot straps.”

The big buyouts also come as equity is under increased scrutiny by shareholders and regulators. Some shareholders have complained that private equity firms have been able to buy public companies at massive discounts and have been able to quickly flip them after larding them up with debt and extracting enormous fees.

The Department of Justice, meanwhile, is looking into whether private equity firms that form consortiums are breaking antitrust laws and trying to drive down buyout premiums.

While it is unclear whether talks between Vivendi and Kohlberg Kravis will resume, the negotiations potentially expose Vivendi to questions about its future.

The company initiated the discussions, people involved in them said, and then broke off the negotiations after several weeks of intense meetings.

Vivendi had previously rejected an informal takeover offer last May from Sebastian Holdings, a Norwegian investment company that had expressed interest in buying Vivendi and breaking it up.

Kohlberg Kravis had a special relationship with Vivendi; Henry Kravis’s wife, Marie-Josée Kravis, had been a member of Vivendi’s supervisory board, though she stepped down from it last March.

While it was unclear whether K.K.R. had formally lined up other private equity firms to join a consortium, it had been in discussions with J. P. Morgan Chase and Citigroup about financing the transaction.

A spokeswoman for Kohlberg Kravis declined to comment. A spokesman for Vivendi could not be reached.

Vivendi Universal has gone through more high-profile marriages and breakups than some Hollywood starlets. The media conglomerate’s businesses include Universal Music, the world’s biggest record company, and a 20 percent stake in NBC Universal, the film and television arm of General Electric.

Among its other holdings are a majority interest in SFR, France’s largest mobile telephone operator, and Canal Plus, the French pay-television channel, which last month won the right to merge with a satellite television rival, TPS. This fall, Vivendi paid more than $2 billion to combine Bertelsmann’s music publishing library with its Universal Music unit, making it the world’s largest recording company with artists as varied as Elton John to B. B. King.

The deal seemed to usher in a new era at Vivendi, as the company’s new management team signaled that it was putting its turbulent past under Jean-Marie Messier behind it as it pursued a focused strategy of building its four main businesses: telecommunications, video games, music and pay television.

Like other media companies, it is also trying to reap the benefits of cross-promoting its content among those various platforms.

Mr. Messier, its controversial former chief executive, loaded the company with debt with several big acquisitions made during the dot-come boom. But with the company teetering on the edge of bankruptcy in 2002, he was ultimately forced out.