SIOUX CITY, Iowa — Republican presidential contender Mitt Romney, seeking to protect his lead and fend off challenges from rivals in this early-voting state, assailed Rudy Giuliani and Mike Huckabee over supporting tuition breaks and broader sanctuary for illegal immigrants or their children.

The former Massachusetts governor singled out two of his Republican opponents and likened them to Democratic front-runner Hillary Rodham Clinton, saying Tuesday: "There are those people in both parties who are in a sanctuary state of mind, who believe in sanctuary cities, who believe in policies which are sanctuary in nature."

In campaign appearances and advertisements in Iowa and elsewhere, Romney is increasingly using illegal immigration to differentiate himself from the rest of his opponents. The issue is particularly salient in Iowa's ultra-conservative western region, given the influx of immigrants coming to work in fields and factories in recent years.

Just weeks before voting begins, Romney is looking to solidify his double-digit advantage in polling in the leadoff caucus state while curbing Huckabee's recent rise in surveys and among religious conservatives. He also wants to prevent Giuliani from mounting a more serious challenge.

Going after both, Romney contended that Huckabee, the former Arkansas governor, fought for tuition breaks for children of illegal immigrants in his state, while Giuliani, the former New York mayor, provided tuition breaks at the City University for illegal immigrants. He said that Clinton, too, backs such breaks.

"Giving a better deal to the children of illegal aliens than we give to U.S. citizens from surrounding states is simply not fair and not right," Romney told reporters during a one-day visit.

In turn, Huckabee said in a phone interview with The Associated Press: "The attacks from a guy who has sanctuary cities in his state is interesting." Huckabee said he backed a bill in Arkansas — and would do so again — that gave children of illegal immigrants "the opportunity to be awarded for academic achievements" based on merit provided they were in the process of applying for citizenship.

"Why would you penalize the children for the crime of the parents?" Huckabee asked.

Also responding to Romney, Giuliani spokeswoman Maria Comella accused him of ignoring his own record as governor while he campaigns for president. "Under Governor 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," she said.

During his time as governor, at least three Massachusetts cities offered sanctuary to illegal immigrants.

Speaking to reporters, Romney noted that he vetoed a bill the Massachusetts Legislature passed that would have allowed children born to illegal immigrants to get a tuition break in state schools. "Illegals do not get a break in our schools," he said.

While he focused on Huckabee and Giuliani, Romney broadened his criticism to include opponent John McCain, saying, "He is somebody who has taken the wrong side on this issue as well."

Romney didn't mention Fred Thompson, the former Tennessee senator who is billing himself as a consistent conservative and a staunch opponent of illegal immigration as he steps up efforts in Iowa to try to reverse a downward spiral.

Asked whether he agreed with Thompson's record on immigration, Romney sidestepped.

"He wasn't a governor or a mayor, and so he didn't put in place policies that would have affected, for instance, tuition breaks to illegals or driver's licenses," Romney said. "He was elected to the Senate, went to the Senate. What did he do during that time period? I just don't know. It doesn't stand out as an effort that he made."

On other issues, Romney:

— Shrugged off the National Right to Life Committee's endorsement of Thompson, saying: "You always like all the endorsements you can get but you can't get them all." He took the opportunity to mention Giuliani's support for abortion rights.

— Appeared to distance himself from the Bush administration's policy banning the photographing of coffins returning from war. "I don't see any particular reason to have that policy, but I haven't really heard both sides of it," he said, adding he wouldn't find it offensive for people at an airport terminal to snap a photo.