U.S. senators are voicing sharp divisions on what should become of millions of illegal immigrants, as they consider a variety of proposals to reform America's immigration system. Meanwhile, immigrant-rights rallies continue, with a march in New York City.

In what has emerged as a fierce and polarizing immigration debate, there is one idea that senators agree on: that the United States must have greater control over its borders, through which hundreds of thousands of illegal aliens pass every year. But there is little agreement on how to accomplish that goal, or how to treat the more than 11 million undocumented aliens estimated to be living in the United States.

Barack Obama

Speaking on ABC's This Week program, Illinois Democratic Senator Barack Obama said he favors a three-step approach.

"Improving border security, tightening employer sanctions [penalties for those who hire illegal workers]. The second provision is providing a pathway to citizenship. We have 11 to 12 million undocumented workers in the country. We want to regularize their lives. The third component is a guest worker program," said Obama.

Also appearing on This Week, Republican George Allen of Virginia said there must be no reward for breaking U.S. laws.

"There is a consensus in America that we need to secure our borders," commented Allen. "If we have a reward of illegal behavior, all we will get is more illegal behavior. There are many people who have come into this country legally."

Backers of the citizenship path counter that illegal aliens would have to pay fines and submit to background checks, among other steps, in order to be considered for eventual citizenship.

Senator Obama says it is the only practical option available.

"The notion that somehow these 12 million people are going to get on a bus and go back across the border just is not realistic," he added.

But Senator Allen disagrees, arguing that, if labor laws prohibiting the employment of undocumented workers were rigorously enforced, illegal aliens would return to their native lands on their own.

"The main point is: enforce the law. Right now, it is illegal to hire those who are [here] illegally. And if there is a workable, efficient, practical way of hiring legal workers in this country, employers will do that. Then, those who are here illegally will see that they cannot find work in this country, and they are going to have to leave," he argued.

Yet U.S. business groups warn of dire consequences for the U.S. economy, if the supply of inexpensive labor from abroad were to disappear.

Immigrant-rights groups point out that many illegal aliens have U.S.-born children, who are American citizens, and that forcing the parents to leave the country would tear families apart.

Protesters pray during the The Great Walk in Solidarity With Immigrants in New York, April 1, 2006,

A bill that passed the U.S. House of Representatives would designate illegal aliens as felons, and mandate constructing more than 1,000 kilometers of new fence along the U.S. - Mexico border. What action the Senate may take is unclear, but many immigrants and immigrant-rights supporters have vociferously protested the House legislation as an abdication of America's history as a welcoming nation.

Sunday, demonstrators marched across New York's Brooklyn Bridge into Manhattan. Dozens of other demonstrations have been held across the country in recent weeks.