After declaring Louisiana a disaster area Monday so it could quickly get federal help, Obama declared a state of emergency for Mississippi Tuesday.
The White House said the action authorizes the Department of Homeland Security and the Federal Emergency Management Agency to coordinate all disaster relief efforts, and to provide assistance for required emergency measures under federal law.
Forecasters expect Isaac to strike New Orleans Wednesday on the anniversary of Hurricane Katrina, which killed about 1,800 and caused billions in damage.
Obama Tuesday told reporters at the White House he wanted "to encourage all residents of the Gulf Coast to listen to your local officials and follow their directions, including if they tell you to evacuate. We're dealing with a big storm and there could be significant flooding and other damage across a large area. Now is not the time to tempt fate. Now is not the time to dismiss official warnings."
The president said he was getting updates from the Department of Homeland Security, the Federal Emergency Management Agency and the National Hurricane Center in Miami "on preparations that are under way in the Gulf [of Mexico region]."
"This storm isn't scheduled to make landfall until later today, but at my direction FEMA has been on the ground for over a week working with state and local officials in areas that could be affected -- from Puerto Rico and the U.S. Virgin Islands to Florida, and more recently, Louisiana, Alabama and Mississippi," he said.
"Yesterday I approved a disaster declaration for the state of Louisiana so they can get the help that they need right away, particularly around some of the evacuations that are taking place. And right now, we already have response teams and supplies ready to help communities in the expected path of the storm."