The Homeland Security Department (searchwill train as many as 5,000 customs and immigration agents to serve as air marshals when U.S. airliners are especially threatened by terrorists, officials said Tuesday.

The backup air marshals would supplement the current corps of armed, undercover federal officers who travel on flights deemed at risk by security officials. In periods when intelligence suggests a heightened threat, Homeland Security would be able to dispatch marshals on more flights.

"With this single move we will be able to deploy more than 5,000 additional armed federal law enforcement agents to the skies, when needed," Homeland Security Secretary Tom Ridge (searchsaid in a speech Tuesday at the American Enterprise Institute in Washington.

Homeland Security officials said immigration and customs agents who man inspection stations at U.S. borders or at ports would not be trained as air marshals, so as to keep those stations from losing personnel during terrorist threats. Instead, the reserve air marshals would be drawn primarily from investigators and other enforcement officers.

The plan will take the existing air marshal program out of the Transportation Security Administration (search) and place it under the Bureau of Immigration and Customs Enforcement. Both are part of Homeland Security.

Some Democrats in Congress suggested the bureaucratic shuffle was an attempt to hide inadequate financial arrangements for aviation security.

Wisconsin Rep. David Obey, ranking Democrat on the House Appropriations Committee, said the change will make the air marshals more flexible but doesn't solve the problem. "We have too few people in these positions," he said.

Rep. Carolyn Maloney, D-N.Y., chairwoman of the Democratic Task Force on Homeland Security, suggested the air marshals might be taken out of the Transportation Security Administration because it has a billion-dollar budget shortfall.

"Are they doing so to save money?" Maloney said. "The real solution is not to rearrange the deck chairs, but to reinforce defenses by getting the necessary resources to each homeland security program."

Earlier this year, lawmakers criticized the Bush administration when they learned the Transportation Security Administration wanted to cut 20 percent of its money designated for the air marshal's program to plug other budget holes. Many vowed to block any such funding cuts.

The air marshal program was nearly nonexistent at the time of the Sept. 11 attacks. Only 32 agents were employed then, but the number was dramatically increased afterward. The exact number is classified.

In the 1970s, when teams of sky marshals were created to thwart hijackings, they were part of the U.S. Customs Service (search). The Transportation Security Administration was created after the Sept. 11, 2001, attacks and took over the air marshal program, along with airport screening and other transportation security operations.

On Tuesday, Ridge also detailed his department's efforts to:

--Consolidate the three usual border inspections into one, in which a single primary inspector would handle immigration, customs and agricultural checks. If a question should arise about a traveler, a secondary inspection would be conducted by another agent. The consolidation would allow more agents to be deployed for the more precise secondary inspections "targeting our resources toward those passengers with suspicious indicators," the department said.

--Establish a network of secure communications linking the department and the states, videoconference and telephone lines to be used for sharing information about threats.

--Make it easier for states to obtain anti-terrorist and security grants. The department will ask Congress to centralize under one agency the grant application process, which now is spread across numerous agencies.