Republican presidential candidate Mitt Romney said Thursday that former New York Mayor Rudy Giuliani is partly responsible for the vast number of illegal immigrants living in the U.S. today. As mayor of the nation's most populous city for eight years, Giuliani created an environment that lured illegal workers by sheltering them from legal risk, Romney said. "He welcomed illegal aliens to the city," Romney told reporters after appearing before about 200 supporters at a hotel. "That sanctuary state of mind is one of the reasons we have so many illegal immigrants in our country today."

Giuliani's campaign didn't directly respond to the criticism, saying that the former Massachusetts governor is trying to radically recast his record on immigration.

"Under Gov. Mitt Romney the number of illegal immigrants skyrocketed, while he recommended millions of dollars in state aid to numerous sanctuary cities and to companies employing illegal immigrants, not to mention the illegals working on his own lawn," Giuliani spokeswoman Maria Comella said in a statement.

Romney has been raising illegal immigration in campaign appearances and advertisements to draw distinctions between himself and other GOP contenders. The issue is particularly salient in Iowa's conservative western region, given the influx of immigrants coming to work in fields and factories.

In his remarks to supporters, Romney said the nation values legal immigration but must stop programs that reward or entice illegal workers to enter the U.S. For example, he said, it was a mistake to grant driver's licenses to illegal workers, a day after Gov. Eliot Spitzer backed away from a plan to do that in New York.

Romney has also proposed bolstering border fence patrols and imposing tax penalties on employers who hire illegal aliens after creation of an employment eligibility card.

On other issues, Romney didn't answer directly when asked if he would consider it bigotry if someone refused to vote for him because of his Mormon faith.

"I respectfully acknowledge the rights of people to choose presidents any way they want to," Romney said.

Many voters, he said, "respect the fact that I'm a person of faith."

Written By MICHAEL R. BLOOD