The White House escalated its response Thursday to the growing oil spill in the Gulf of Mexico, and a local official said the massive slick is projected to reach the Louisiana coast late Thursday.

In an afternoon appearance in the Rose Garden, President Barack Obama promised to use "every single available resource" of government to help with the spill, which could be one of the largest in U.S. history. The U.S. military began mobilizing for what could be a major effort to prevent environmental damage to Louisiana and other states.

The oil "is already in state waters" and will reach the Pass-a-Loutre Wildlife Management Area, near the southernmost tip of the state later Thursday, Plaquemines Parish President Billy Nungesser said after a meeting with council members and a congressman to discuss the emergency.

The prospects for slowing the spread of the oil appear dim, and the slick threatens to cause significant environmental damage and disruption to business along the Gulf Coast. In Louisiana, Gov. Bobby Jindal declared a state of emergency Thursday to aid state response and asked the Coast Guard and BP PLC to deploy more resources to the state.

It appears that the oil well, damaged after a Transocean Ltd. rig hired by BP exploded and sank last week, is leaking 5,000 barrels of oil a day, five times the rate thought earlier this week, officials said. The slick spans about 600 square miles.