Federal officials vowed urgent support on Sunday for a region devastated by the deadliest U.S. natural disaster since Hurricane Katrina, even as they acknowledged recovery would not be quick or easy.

President Barack Obama's administration is trying to show an effective response to the storms and twisters that killed about 350 people last week in seven southern states, reduced neighborhoods to rubble and caused damage expected to run into billions of dollars.

Obama visited Alabama on Friday and Homeland Security Secretary Janet Napolitano, Agriculture Secretary Tom Vilsack and the administrator of the Federal Emergency Management Agency, Craig Fugate, toured damage on Sunday.

"I don't think words can fairly express the level of devastation here. I am not articulate enough," Napolitano said after seeing how killer storm winds had torn through Pratt City, Alabama.

Later in Smithville, Mississippi, Napolitano said the visit had offered an acute sense of urgency about the need to help communities "come to grips and recover" from the disaster.

"This is not going to be a quick comeback or an immediate one but it will be, in my view, a complete one when all is said and done," she said.

Obama's predecessor, former President George W. Bush, was sharply criticized for the federal response after Hurricane Katrina raked the Gulf Coast and flooded New Orleans in 2005.

The Republican governors of Alabama and Mississippi both spoke highly of Washington's response to the latest disaster.

"When you see local, state and federal people cooperating like this, it really makes a difference," Alabama Governor Robert Bentley said on CBS's "Face the Nation" program.

But the administration's performance over the storm has not won universal praise. Texas Governor Rick Perry criticized the White House for not responding to a request for disaster aid for his state, where wildfires have scorched nearly 2 million acres.

"You have to ask, 'Why are you taking care of Alabama and other states?' I know our letter didn't get lost in the mail," Perry, a Republican and frequent government critic, said last week.

Alabama was the worst-hit state in last week's storms, with 250 people killed. Elsewhere, 101 people died in Mississippi, Tennessee, Arkansas, Georgia, Virginia and Louisiana.

About 1,700 people were injured in Alabama alone and others were missing after tornadoes crushed homes, flipped cars upside down and tore children from their parents' arms.

To help people get back on their feet, the Department of Agriculture will make homes in rural areas available for rent, said Vilsack.

The U.S. Small Business Administration announced it would make loans of up to $200,000 available to homeowners and up to $2 million for small businesses. It would also make $80 million available in block grants to states.

Katrina devastated New Orleans, killed more than 1,800 people and left thousands of people stranded for days on rooftops, in the open or in chaotic public buildings.

FBI officers, FEMA officials, state troopers, police, sheriffs, firefighters, and officials of the U.S. Fish and Wildlife service worked with many local volunteers to clear roads and debris on Saturday.

"My friend and her boy died right over there. This is what I can do for her from my heart," said Carlos Carabez, who was sawing a fallen tree into pieces so it could be hauled away.

Bentley declared Sunday a day of prayer in Alabama, a relatively poor and politically conservative state in a region where evangelical churches play a powerful social role.

Several churches were torn down by the storms, including Bethel Baptist church, an African American church in Pratt City outside Birmingham with a congregation of 5,000. On Sunday, the church held services at a local convention center.

"This service is our response to tragedy. It shows that we are not victims. We are victors. We are visible victors," pastor T.L. Lewis said in an interview.

The death toll from last week, which is still expected to rise, was the second-highest recorded from tornadoes in U.S. history. In 1925, 747 people were killed after twisters hit the midwestern states of Missouri, Illinois and Indiana.

Unlocking federal assistance, Obama on Friday signed major disaster declarations for Mississippi and Georgia, adding to the one already signed for Alabama.

(Additional reporting by Tami Chappell in Birmingham, Verna Gates in Phil Campbell; writing by Matthew Bigg; editing by Mohammad Zargham)