A group of oil companies led by Exxon says it has built a system that can stop an undersea oil spill within weeks, a critical step in the effort to resume drilling in the deepest parts of the Gulf of Mexico.

The group announced Thursday that it has cobbled together enough equipment and support vessels to handle a spill similar to BP's gusher last year, which took almost three months to plug. A more robust network with expanded capabilities should be finished early next year.

Regulators have demanded that oil companies demonstrate the capability to contain an underwater well blowout before granting permits to drill in Gulf waters deeper than 500 feet.

Exxon says this system meets that demand, and says it doesn't expect any problem obtaining government approval.