More than two months after the Obama administration lifted its ban on drilling in the deep-water Gulf of Mexico, oil companies are still waiting for approval to drill the first new oil well there. Experts now expect the wait to continue until the second half of 2011, and perhaps into 2012.

The administration says it is simply trying to enforce new safety rules adopted in the wake of the April 20 explosion of the Deepwater Horizon drilling rig, which killed 11 workers and set off the worst offshore oil spill in U.S. history. Environmental groups say the administration is right to take its time because the Gulf disaster exposed the risks of offshore drilling.

But the delay is hurting big oil companies such as Chevron Corp. and Royal Dutch Shell PLC, which have billions of dollars in investments tied up in Gulf projects that are on hold and are paying hundreds of thousands of dollars a day for rigs that aren't allowed to drill. Smaller operators such as ATP Oil & Gas Corp. , which have less flexibility to focus on projects in other regions, have been even harder hit.

The impact of the delays goes beyond the oil industry. The Gulf coast economy has been hit hard by the slowdown in drilling activity, especially because the oil spill also hurt the region's fishing and tourism industries. The Obama administration in September estimated that 8,000 to 12,000 workers could lose their jobs temporarily as a result of the moratorium; some independent estimates have been much higher.

The slowdown also has long-term implications for U.S. oil production. The Energy Information Administration, the research arm of the Department of Energy, last month predicted that domestic offshore oil production will fall 13% this year from 2010 due to the moratorium and the slow return to drilling; a year ago, the agency predicted offshore production would rise 6% in 2011. The difference: a loss of about 220,000 barrels of oil a day.