Update | 8:28 p.m. General Electric has reached a tentative agreement to buy Vivendi’s 20 percent stake in NBC Universal for about $5.8 billion, helping clear the path to a sale of the television and movie company to Comcast, people briefed on the matter told DealBook.

But much remains to be negotiated, these people warned. The Vivendi agreement values NBC Universal at $29 billion, less than the $30 billion or so that G.E. and Comcast had agreed to last month.

Harmonizing the two values, as in so much of the talks over NBC Universal, may take days to do, and these people cautioned that a deal may not be reached.

Still, many analysts and people close to the talks expect a deal to be forged soon, and with it a reshaping of the entertainment industry.

The groundwork for the tentative pact between G.E. and Vivendi was laid out last week, when G.E.’s chief executive, Jeffrey Immelt, met in person with his counterpart at Vivendi, Jean-Bernard Lévy, in Paris, these people said.

If it holds, the agreement would conclude weeks of hardball negotiations between G.E. and Vivendi over an alliance first forged in 2004. Resolving the issue of Vivendi’s stake is crucial to completing the G.E.-Comcast deal. But the French company took a tough stance, brandishing its option of holding an initial public offering for its stake rather than selling it back to G.E.

Under the current outlines of the agreement between G.E. and Comcast, NBC Universal would be put into a new joint venture, between the two giants. Comcast would pour billions of dollars in cash and its own cable channels for a 51 percent stake, while G.E. would hold an initial 49 percent and contribute about $12 billion in debt.

G.E., which has owned NBC for more than two decades, is expected to eventually sell its ownership interest to Comcast over the next several years.

– Michael J. de la Merced and Bill Carter