(Updates with additional details on kill operation from BP executive.) HOUSTON (Dow Jones)--BP PLC'S (BP, BP.LN) attempt to kill the well that spewed millions of gallons of oil in the Gulf of Mexico will be delayed until early next week, as the company cleans up rock debris found at the bottom of a relief well, company officials said Friday. The start of the so-called static kill, previously scheduled for late Sunday or early Monday, is now estimated to start on late Monday night or some time Tuesday, BP Senior Vice President Kent Wells said. The reason for the delay is that rocks fell into the depths of a relief well that is to intersect the damaged Macondo well, and they must be removed before work can continue there. Wells said that the static kill is "ready to go," and that BP has amassed thousands of barrels of drilling fluid in surface ships. Wells said that the well has a capacity of 2,000 barrels, but BP has 12,000 barrels of drilling fluid available in vessels around the Deepwater Horizon site. U.S. authorities say that inserting a pipe down the relief well is necessary to reinforce it before BP can flood the neighboring damaged well with drilling mud to permanently kill the spill. The wells are separated by a 4.5-foot wall of rock. Once the Macondo well is flooded from the top with mud and cement, BP will attempt to flood it from the bottom via the relief well. The relief well is scheduled to intersect the Macondo well on Aug. 11 or 12, Wells said. In a teleconference call on Friday, the head of the federal oil spill response effort, retired Coast Guard Admiral Thad Allen, said that cleaning the sedimentary debris out of the relief well "is not a huge problem." The debris fell after a drilling rig had to quickly evacuate the well last week, as tropical storm Bonnie approached, without being able to complete the casing of the well. Casing prevents rocks and other sediments from falling into the well. BP said Friday that oil remained shut in at the damaged well, and pressure kept building slowly, an indication that the well is in good shape and hydrocarbons are not seeping out from the sides. -By Angel Gonzalez, Dow Jones Newswires; 713-547-9214; angel.gonzalez@dowjones.com (END) Dow Jones Newswires July 30, 2010 16:59 ET (20:59 GMT)