"The bad news is that this is some big monster," Trump told reporters at the White House, saying damage from the storm would be very costly.
"Right now, we are worried about lives, not cost," Trump said after returning from Camp David, the presidential retreat in Maryland where he monitored the storm and met with his Cabinet.
The path of the storm, tracking the west coast of Florida, meant it might be less destructive than it would otherwise have been, Trump said, noting the next five or six hours would be critical.
"I hope there aren't too many people in the path," he said. "You don't want to be in that path."
The U.S. House of Representatives canceled votes scheduled for Monday because of the hurricane.
Trump said the U.S. Coast Guard had been heroic and that the Federal Emergency Management Agency was doing a good job to help coordinate the response with states. He added, however: "I think the hard part is now beginning."
Trump has offered the full resources of the federal government to Florida and the affected states, Vice President Mike Pence told reporters during a visit to FEMA's Washington headquarters on Sunday.
On Sunday, Trump also issued a disaster declaration for the U.S. territory of Puerto Rico, and expanded federal funds available to the U.S. Virgin Islands in the aftermath of Irma, the White House said.
Trump owns a resort in Palm Beach, Florida, where he has often traveled during his presidency, as well as three golf courses in the state.
He told reporters he hoped to travel to the state soon.
"We're going to Florida very soon," Trump said.
(This story has not been edited by NDTV staff and is auto-generated from a syndicated feed.)