HOUSTON  BP engineers struggled Friday to plug a gushing oil well a mile under the sea, but as of late in the day they had made little headway in stemming the flow.

Amid mixed messages about problems and progress, the effort  called a “top kill”  continued for a third day, with engineers describing a painstaking process of trying to plug the hole, using different weights of mud and sizes of debris like golf balls and tires, and then watching and waiting. They cannot use brute force because they risk making the leak worse if they damage the pipes leading down to the well.

Despite an apparent lack of progress, officials said they would continue with the process for another 48 hours, into Sunday, before giving up and considering other options, including another containment dome to try to capture the oil.

President Obama, who visited the Gulf Coast on Friday, spoke broadly about the government’s response to the environmental disaster, saying that “not every judgment we make will be right the first time out.”