BOSTON (Reuters) - A top U.S. Coast Guard official has told BP Plc the company’s plans to contain the gushing oil spill in the Gulf of Mexico do not go far enough or contain enough back-up measures.

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“BP must identify in the next 48 hours additional leak containment capacity that could be operationalized and expedited,” Coast Guard Rear Admiral James Watson said in a letter to BP dated June 11.

Watson, the federal on-scene coordinator for spill response, noted estimates of the amount of oil leaking from BP’s damaged well have been raised sharply.

He did not suggest what actions could be taken if the 48-hour deadline was not met.

Watson’s letter was a response to one from BP that described the company’s multi-phase plans to contain the spill, involving several elements to be phased in by mid-July.

“The combination of Phase One and Two results in a capacity of 40,000 to 50,000 barrels of oil per day,” said Doug Suttles, BP’s chief operating officer.

“We believe this plan is responsive to your order,” Suttles said, adding the company cannot assure that “complete collection rates” are guaranteed.

Not good enough, said Watson.

“You indicate that some of the systems you have planned to deploy may take a month or more to bring online. Recognizing the complexity of this challenge, every effort must be expended to speed up the process,” he wrote.

“I am also concerned that your plan does not go far enough to mobilize redundant resources in the event of an equipment failure with one of the vessels, or some other unforeseen problem.”