With Japan reeling from a massive earthquake and subsequent tsunami, a vet­eran government watchdog warned Thursday that the Federal Emergency Management Agency “is in a constant state of flux” and needs to do even more to coordinate with state and local officials.

The agency, widely panned for its response to Hurricane Katrina in 2005, also needs more personnel to handle a growing workload as state and local governments trim emergency management budgets and should upgrade its computer systems, according to Richard L. Skinner, the former inspector general for the Department of Homeland Security who authored a progress report on the agency before retiring in January.

He spoke Thursday at a Senate hearing — originally scheduled for this past fall but postponed until this week — as the events in Japan raise concerns about preparedness efforts in the United States.

“Japan was considered the gold standard of earthquake preparedness, but even so, this earthquake . . . and the waves of disaster it set off, have exceeded the country’s preparations,” said Sen. Joseph I. Lieberman (I-Conn.), chairman of the Senate homeland security committee. But five years after Katrina, “I am convinced FEMA has become stronger and more capable,” Lieberman said at the hearing.

The agency spends about $4.3 billion annually on disaster response, mostly by distributing money through assistance programs, and many of its roughly 4,000 employees are “dual-hatted.”

“As more disasters are declared and disasters stay open for longer periods of time, more FEMA staff resources are diverted from planning and preparedness efforts,” the report said.

Skinner credited FEMA for gaming out several potential natural-disaster scenarios across the country, including plans for major hurricanes in Hawaii and Florida, typhoons in Guam and earthquakes in the San Francisco Bay Area, in Southern California, in northwest Nevada and along the New Madrid fault lines in the Midwest.

Despite progress, changes continue “at a snail’s pace,” Skinner said.

“There is a good chance that we will be talking about these issues five or 10 years from now,” he said.

FEMA Administrator W. Craig Fugate generally agreed with Skinner but disputed suggestions that the agency is moving too slowly. “We’ve made significant improvements with the tools we have,” Fugate said. “There is much more to be done.”

The agency is preparing for a mid-May “National Level Exercise” that will bring together federal, state and local officials to rehearse the potential aftermath of a major earthquake’s impact on eight Midwestern states across the New Madrid seismic zone. Between 2005 and 2010, the agency spent $218 million on similar exercises.

Some state and local officials — including former Arizona governor Janet Napolitano, now the Homeland Security secretary — have criticized the rehearsals as a costly distraction, but the drills remain a top priority for Fugate, according to aides.

“We recognize that in large-scale disasters, government cannot do it alone, which is why we are constantly working with the entire federal family, state, local and tribal governments, faith-based and nonprofit organizations, and especially the public to plan and prepare, so we can respond as one team,” FEMA spokesman Brad Carroll said before Thursday’s hearing. Many of the agency’s top leaders, including Fugate, are experienced as emergency managers at the state and local level, Carroll said.

The agency also said Thursday it has recouped $47 million in disaster relief funds improperly paid to victims of hurricanes Katrina and Rita. Skinner’s office said in January that the agency had failed to recoup about $643 million in funds improperly distributed to people living in FEMA-funded trailers or who cited the same property when seeking assistance after both storms, despite rules prohibiting them from doing so.