Pentagon spokesman Geoff Morrell said Friday the C-130s are part of the 910th Airlift Wing, which is a reserve unit based in Youngstown, Ohio. The planes are equipped with what is known as the Modular Aerial Spray System (MASS), the same chemical the Coast Guard is using on the oil slick.
The 910th will stage its mission out of Lake Charles, La. Morrell said the planes are able to treat approximately 250 acres per flight and they expect each aircraft to fly three flights per day in support of the Homeland Security-led operation.
Gates gave a verbal "go ahead" to launch the aircraft, Morrell said. This is in addition to the Navy assets being sent to assist.
The contribution is the latest addition to the clean-up of a leak from a blown-out well a mile underwater.
The slick from the April 20 explosion of the oil rig Deepwater Horizon run by BP is five times bigger than first believed.
An oily sheen began reaching the Mississippi River delta late Thursday, lapping the Louisiana shoreline in long, thin lines. Thicker oil was about five miles offshore. Officials have said they would do everything to keep the Mississippi River open to traffic.
The oil slick could become the nation's worst environmental disaster in decades, threatening to eclipse even the Exxon Valdez in scope.
Attorney General Eric Holder announced that he is dispatching a team of attorneys from multiple divisions within the Justice Department to meet with the U.S. attorney in New Orleans to monitor spill, an indication that it is looking at potential legal actions that may be taken.
"The Justice Department stands ready to make available every resource at our disposal to vigorously enforce the laws that protect the people who work and reside near the Gulf, the wildlife, the environment and the American taxpayers," Holder said in a statement.
President Obama said his administration is doing everything it can to help. Currently, the departments of Defense, Justice, Interior and Homeland Security as well as the Environmental Protection Agency and the National Oceanic and Atmospheric Administration are all responding to the leak, which is 5,000 barrels of oil per day.
"There are now five staging areas to protect sensitive shore lines, approximately 1,900 federal response personnel are in the area and more than 300 response vessels and aircraft on the scene 24/7," he said Friday.
The Pentagon spokesman described the clean-up as a "dynamic, changing situation" that Defense Department leadership is constantly evaluating. On Thursday, the Pentagon sent salvage teams, skimmers and about 50 contractors to operate the skimmers.
"As the situation evolves, we will respond as needed," he said.
US Northern Command has liaison officers on site at the DHS Command Centers, working to figure out what the Coast Guard needs. The Coast Guard is working with BP to deploy floating booms, skimmers and chemical dispersants, and has set controlled fires to burn the oil off the water's surface.
Coast Guard Rear Adm. Sally Brice-O'Hara, who is leading the operation, said the response led by the Coast Guard has been rapid, sustained and adapted to the changing threat.
Fox News' Mike Emanuel contributed to this report.