Federal officials announced a plan Thursday to more than double the size of two Northern California marine sanctuaries that would permanently protect the entire Sonoma County coast and part of the Mendocino County coastline from oil and gas drilling.

The National Oceanic and Atmospheric Administration said it will begin a public process to weigh expanding the boundaries of the Gulf of the Farallones and Cordell Bank national marine sanctuaries, which Congress first moved to protect in the 1980s.

"At long last, we're on the road to giving these waters off the Sonoma County coast the protection they need and deserve," said Rep. Lynn Woolsey, a Petaluma Democrat who long fought for greater protection.

Fishing is allowed within the two sanctuaries, but the current boundaries keep nearly 2,000 square miles of ocean off limits to oil drilling and other commercial activities such as seafloor mining and discharges by ocean liners.

If the proposed expansion goes forward, the protected area would grow by 2,700 square miles, meaning the sanctuary boundaries would stretch all the way to Point Arena, which is home to diverse species and a productive ecosystem.

The nation's ocean research agency will review public comments on its proposal to decide whether an expansion should go forward, and if so, will write up a draft environmental impact statement.