Much of the attention has been focused on recovery efforts in Texas, but Louisiana Gov. John Bel Edwards had asked for the declaration and said his state would be in the storm's path for the next week.
Federal officials and lawmakers have yet to calculate the damage from Harvey, which came ashore Friday night as a Category 4 hurricane, and is still pummeling Texas with rainfall.
Edwards sent a letter to Trump on Sunday, requesting he declare an Emergency Disaster effective August 27 for the State of Louisiana as a result of Hurricane/Tropical Storm Harvey.
A wide array of federal agencies, and more than 8,500 federal officials are working in the two states.
Trump's action allows the Federal Emergency Management Agency to coordinate all disaster relief efforts.
Rep. Mike McCaul, R-Tex., chairman of the House Homeland Security Committee Chairman, said Congress may have to address the possible shortage.
"We know that the predicted rainfall from Hurricane Harvey will produce risky flooding across our state, including some of the same areas affected by the 2016 floods", Edwards wrote.
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Harold Henderson has been appointed by National Football League commissioner Roger Goodell to hear the appeal. Elliott had six games for 18 yards and caught two passes for six years in one series of work.
"We've got to pass a supplemental unlike the fight we had for Hurricane Sandy (funding)", Jackson Lee, who is on the Homeland Security Committee, said on CSPAN Monday.
Assistance can include grants for temporary housing and home repairs, low-priced loans to cover uninsured property losses, and other programs to help individuals and business owners recover from the effects of the disaster. "This has caused the extremely slow movement of the storm, moving only around 60 miles, less than 2 miles per hour".
The United States has activated an emergency response program to deploy hundreds of federal employees to the flood-stricken U.S. states of Texas and Louisiana, the Department of Homeland Security said on Tuesday.
On Sunday, Edwards warned Louisiana residents to remain vigilant.
Brock said authorities were anticipating that some 30,000 people would be placed in temporary shelters due to the flooding.
Rep. Clay Higgins, R-La., will also join efforts to get disaster funds if Louisiana needs it, said Andrew David, a spokesman for the congressman. "We will do nothing less to support to the people of Texas in any way that we can as they respond and recover from Hurricane Harvey".