NEW ORLEANS  In another serious setback in the effort to stem the flow of oil gushing from a well a mile beneath the Gulf of Mexico, BP engineers said Saturday that the “top kill” technique had failed and, after consultation with government officials, they had decided to move on to another strategy.

Doug Suttles, BP’s chief operating officer for exploration and production, said at a news conference that the engineers would try once again to solve the problem with a containment cap and that it could take four to seven days for the device to be in place.

“After three full days of attempting top kill, we now believe it is time to move on to the next of our options,” Mr. Suttles said.

The abandonment of the top kill technique, the most ambitious effort yet to plug the well, was the latest in a series of failures. First, BP failed in efforts to repair a blowout preventer with submarine robots. Then its initial efforts to cap the well with a containment dome failed when it became clogged with a frothy mix of frigid water and gas. Efforts to use a hose to gather escaping oil have managed to catch only a fraction of the spill.