The automatic budget cuts set to begin March 1 would force the Coast Guard to slash 25 percent of its air and surface operations and pull ships and personnel from their duties in the Arctic, Department of Homeland Security Secretary Janet Napolitano said Thursday.

At a U.S. Senate Appropriations Committee hearing, Napolitano publicly stated for the first time how sequestration would disrupt her department and the nation's security if Congress does not act to prevent it.

Cutting air and surface operations means the Coast Guard would spend substantially less time interdicting drugs and migrants, patrolling fisheries, ensuring the nation's ports are secure and enforcing laws, Napolitano said.

The Coast Guard also would be forced to reduce its presence in the Arctic by nearly one-third, Napolitano said, and defer "a significant level" of ongoing maintenance and training.

One of three Cabinet secretaries who spoke, Napolitano said sequestration also would undercut gains made in border security, increase wait times at ports and airports and slow commerce, make critical infrastructure more vulnerable, and slow response times during disasters.

U.S. Customs and Border Protection would reduce its work hours by the equivalent of more than 5,000 Border Patrol agents, Napolitano said, and law enforcement personnel on the front lines would be furloughed for up to 14 days.

U.S. Immigration and Customs Enforcement would reduce its operations, too, and would not be able to maintain the detention beds mandated by Congress, she added.

The first round of cuts under sequestration totals $85 billion this fiscal year, with half coming from the Department of Defense and the rest from domestic agencies, followed by $109 billion each year for a total $1.2 trillion in cuts over 10 years.

Sen. Barbara A. Mikulski, D-Md., the committee chairwoman, said the Defense Department and its contractors have been the most vocal in recent months about the impact of sequestration, but she's "deeply troubled" about how it will affect each of the federal agencies and the critical services upon which Americans rely.

Napolitano said communities still recovering from Superstorm Sandy, recent tornadoes and other disasters would be affected by a potential $1 billion cut to the Disaster Relief Fund, and state and local emergency personnel across the country would be laid off because funding for homeland security grants would reach its lowest level in seven years.

"Threats from terrorism and the need to respond to and recover from natural disasters will not diminish because of budget cuts," Napolitano said.

Lt. Paul D. Rhynard, a Coast Guard spokesman, said the Coast Guard would reallocate funds to preserve the most essential operations and would evaluate missions, maintenance and training closely to minimize impacts.

But Napolitano said no amount of planning can mitigate the negative effects of sequestration on the security of the country, and she urged Congress to prevent the cuts to "ensure the safety, security and resiliency of our nation."

j.mcdermott@theday.com