Congress should not split up the Immigration and Naturalization Service when including the embattled agency in a new Homeland Security Department, the Bush administration said Wednesday.

"To make the system work, the right hand of enforcement must know what the left hand of visa application and processing is doing at all times," the president's homeland security adviser, Tom Ridge, told the Senate Judiciary Committee.

The House in April voted to break up the INS into separate agencies dealing with border enforcement and new citizenship. That vote came before the White House effort to move the entire agency into the proposed Cabinet-level department.

Some lawmakers said it sends the wrong message to combine the job of processing legitimate immigrant visas with that of border control in the new department.

Ridge also expressed confidence in changes at the FBI and CIA, investigative agencies that are to remain independent from the new department despite criticism they failed to provide any warning before the Sept. 11 attacks.

"It is essential that reforms in the FBI and the CIA must continue," said Sen. Orrin Hatch of Utah, the committee's top Republican.

Ridge cited steps by the FBI and CIA since Sept. 11, such as better sharing of intelligence information, as evidence they were moving the right direction. He was responding to a question from the committee chairman, Sen. Patrick Leahy, D-Vt., if a new terrorism investigative agency were needed.

Ridge said he thought FBI Director Robert Mueller was "making very aggressive and very positive steps."

The administration wants to combine 100 federal entities with 170,000 employees and total annual budgets of at least $37 billion into one department -- all without spending any extra government money. President Bush does not plan to ask for any money for the new department until the 2004 budget year, which many lawmakers say is not realistic.

Agreeing with them was Comptroller General David Walker, head of the General Accounting Office, the investigate arm of Congress.

Despite possible savings in the long term, he told a Senate Judiciary subcommittee Tuesday, "there will be certain transition costs in the near term associated with setting up the new agency."

Walker also said it will take time to create the department. The White House is encouraging swift passage of legislation setting up the department, and lawmakers are rushing to pass initial versions of the plan by the end of July. But complaints about specific pieces have arisen.

"The magnitude of the challenges that the new department faces will clearly require substantial time and effort, and will take extra resources to make it fully effective," Walker said.

Some lawmakers, health advisers and GAO experts questioned whether public health dangers such as a virulent outbreak of influenza could take a back seat to bioterrorism threats under in the new department.

"It may seriously affect our ability to respond to serious threats to the health of the American people," Rep. Henry Waxman, D-Calif., said Tuesday at a hearing of the House Energy and Commerce oversight subcommittee.

The department will include the Office of Public Health Emergency Preparedness, the Strategic National Stockpile -- which includes packages of pharmaceuticals, antidotes and medical supplies that can be rushed anywhere in the United States within 12 hours -- and several programs within the Centers for Disease Control and Prevention intended to enhance local public health capabilities.

"Although HHS programs are important for homeland security, they are just as important to the day-to-day needs of public health agencies and hospitals, such as reporting on disease outbreaks," said Janet Heinrich, GAO director of public health issues.