Negotiations to end the N.B.A. lockout collapsed again Thursday night, in spectacular fashion, with more acrimony, mistrust and fiery rhetoric, and despite the involvement of a federal mediator.

The talks ended about 7 p.m., after nearly 30 hours spent over three days at a Midtown Manhattan hotel. It is the third time this month that the owners and players have walked away from each other with a feeling that they could not move any further.

The last breakdown led to the cancellation of the first two weeks of the season. This one guarantees that another two weeks, the balance of the November schedule, will be wiped out soon. The prospect of losing the entire season looms ever larger.

“Ultimately we were unable to bridge the gap that separates the two parties,” Adam Silver, the N.B.A. deputy commissioner, said about 30 minutes after the parties separated. He added, “We’re saddened on behalf of the game.”