ROBERT, La. -- It will be at least Tuesday before engineers can shoot mud into a blown-out well at the bottom of the Gulf of Mexico, BP said Friday in yet another delay in the monthlong effort to stop the oil that is washing into wetlands and onto at least one public beach.

A so-called "top kill" has been tried on land but never 5,000 feet underwater, so scientists and engineers have spent the past week preparing and taking measurements to make sure it will stop the oil that has been spewing into the sea for a month. They had hoped to try it as early as this weekend.

BP spokesman Tom Mueller said there was no snag in the preparations, but that the company must get equipment in place and finish tests before the procedure can begin. BP already has three deepwater rigs and other equipment near the blown-out well.

"It's taking time to get everything set up," he said. "They're taking their time. It's never been done before. We've got to make sure everything is right."

Crews will shoot heavy mud into a crippled piece of equipment atop the well, which started spewing after the drilling rig Deepwater Horizon exploded April 20 off Louisiana, killing 11 workers. Then engineers will direct cement at the well to permanently stop the oil.

BP PLC, which was leasing the rig and is responsible for the cleanup, has tried and failed several times to halt the oil.

Chief Operating Officer Doug Suttles said Friday that a milelong tube inserted into the leaking pipe is sucking about 92,400 gallons of oil a day to the surface, a figure much lower than the 210,000 gallons a day the company said the tube was sucking up Thursday. Suttles said the higher number is the most the tube has been sucking up at any one time, while the lower number is the average.

The company has conceded that more oil is leaking than its initial estimate of 210,000 gallons a day, and a government team is working to get a handle on how much is flowing.