The Obama administration has approved permits necessary for Royal Dutch Shell PLC to begin limited exploratory oil drilling off Alaska's northwest coast.

The Bureau of Safety and Environmental Enforcement says it's issued "conditional approval" of two permits for drilling in the Chukchi Sea.

The permits are for drilling only on the top sections of wells. Shell can't drill into oil-bearing zones at this stage because it doesn't currently have certain emergency response equipment on site.

Some environmental groups worry that the Arctic's remoteness and rugged conditions will hamper cleanup in the event of a spill.

Proponents say drilling can be conducted safely with existing technologies. They say future production -- decades from now -- will help sustain the country's energy needs and limit reliance on imports.