Mayor Giuliani is wading into the debate over America’s immigration policy with the argument that the comprehensive approach being pursued by the Senate is better for American security than what he called the “punitive” approach being pressed by the House of Representatives.

President Bush and Senator McCain have been pushing what they call a “comprehensive” approach to immigration law that would step up enforcement of the borders but also provide a path to citizenship for illegal aliens and those outside America who might initially enter under a proposed “guest worker” program. Some others Republicans favor an approach that emphasizes enforcement alone.

The immigration debate flared again yesterday in the Senate when Republicans, over the objection of Senator Clinton, voted to reallocate $1.9 billion that Mr. Bush had requested for use to fight the war in Iraq and instead spend the money on building a fence to keep out immigrants from Mexico.

Mr. Giuliani, who is stoking speculation about whether he’ll run for president in 2008 with his plans to visit the early caucus state of Iowa on May 1, took the Bush-McCain approach but sought to justify it on the national security grounds often cited by proponents of the enforcement-only approach.

“How do we create more security for the United States?” he asked in remarks at the Manhattan Institute’s Alexander Hamilton dinner on Tuesday night in Midtown. “To deal with it in a punitive way is actually going to make us considerably less secure.”

The House legislation’s approach of making illegal immigration a felony subject to five years in prison “would become a law that is honored in the breach and it could not possibly be enforced,” Mr. Giuliani said.

“I think the compromise the Senate was looking at, something along those lines makes sense.” Mr. Giuliani said. He said if immigrants are identified using new fingerprint and photograph technology or special identification cards, they can be identified and become taxpayers, so that it is “much harder for terrorists to hide.”

The former mayor devoted the rest of his remarks to thanking the Manhattan Institute for many of the ideas that he implemented as mayor. He also spoke of how the Kennedy, Reagan, and Bush tax cuts had been followed by economic growth. He said America needs to stay on offense against terrorism. “We’re going to be in this struggle for quite some time,” he said.