Very few offshore oil and natural gas drilling rigs will actually resume activity within the first month the deepwater drilling moratorium is lifted in the Gulf of Mexico, a top Interior Department official said Monday.

"Even when the moratorium is lifted, you won't see drilling going on the next day or even the next week," Michael Bromwich, head of the Interior Department's new Bureau of Ocean Management, Regulation, and Enforcement said during testimony in front of the Oil Spill Commission on Monday.

He said it would be difficult for the oil and gas industry to comply with new safety requirements, which he deemed both "appropriate and necessary." These include identifying worst-case scenarios and preparing spill response plans.

The bureau's report on the moratorium will include rules and recommendations for offshore drilling and should be out this week, Bromwich said.

Interior Secretary Salazar, who also testified at the hearing Monday, said he looks forward to scrutinizing the options presented, as mounting pressure comes from Congress to lift the ban early, before it's scheduled to end in late November.

Sen. Mary Landrieu, D-La., has been one of the most outspoken critics of the administration's moratorium. In a letter to Senate Majority Leader Reid late last week, she said she would block the confirmation of the new OMB director until the ban is lifted or "significantly modified." Her Republican counterpart from Louisiana, Sen. David Vitter, supported her effort.

Salazar underscored what he has said since oil began pouring into the Gulf of Mexico in April -- that safety is paramount. The Interior Department's one goal, Salazar said, is "to be able to move forward in a manner that will protect the workers and the environment."