Proposed changes to US immigration law unveiled on Monday could be the answer to the prayers of illegal immigrants like Maria Duran, but she is waiting to see the details.

A bipartisan group of Republican and Democrat senators announced "tough but fair" steps that they hoped could be passed by Congress this year to give 11 million illegal immigrants a chance to eventually become American citizens.

Activists like Duran, who sat up all night with others at a prayer vigil for immigration reform outside the capitol building in Phoenix, Arizona, were pleased but cautious.

"It's the best moment for immigration reform in years, but we need to see more details," said the 50-year-old homemaker, who left Mexico to live in the United States 28 years ago, but still does not have legal status.

The proposed steps are part of the first concerted drive for comprehensive immigration reform since a similar overhaul was defeated by Republicans in Congress in 2007.

It would offer probationary legal status to immigrants who register with the government and pay a fine and any back taxes.

They will also have to learn English, continue to pay taxes and demonstrate a work history in the United States to apply for legal permanent residency.

However, many of the details still need to be worked out and the proposal also seeks to ensure as a first step that the porous border with Mexico is secure and that foreigners in the United States temporarily return home when their visas expire.

Some activists were encouraged by the level of bipartisan support from the four Democrat and four Republican senators who put forward the proposal. They include Charles Schumer, a New York Democrat, and John McCain, a veteran Arizona Republican.

But they also worried that the proposal made tightening enforcement - including adding agents and surveillance systems to the southwestern border - a precondition for all other measures in the package.

"It's really heavy on enforcement. That has always been one of the wedge issues in the community for activists," said Gaby Pacheco, a campaigner in Florida who was brought to the United States from Ecuador at the age of eight.

While the government's own figures showed arrests on the southwest border at a 40-year low in 2011 and deportations at a record high, Pacheco said, "I don't think Republicans are ever going to be satisfied with enforcement measures."

'AMNESTY' OR 'EARNESTY'?

For Juana Garcia, a 27-year-old illegal immigrant from Mexico working in agriculture, reform could ease the fear she and her husband have of deportation and being separated from their five children - all of whom were born in the United States and therefore have citizenship.

The pair are seasonal workers who drive to Wisconsin to work the crops there before returning to Florida's strawberry fields and orange groves - all the while worried that they will be pulled over for a traffic stop and detained.

Garcia, speaking in Spanish, said she has no problem with provisions requiring immigrants to pay fines and back taxes before getting a green card. But she said that while immigrants want to learn English, they may need help finding time or child care to attend classes after labouring in the fields all day.

Arizona Governor Jan Brewer, a Republican whose support for her state's tough crackdown on illegal immigrants in 2010 made her a major White House antagonist on the issue, gave the proposal a cautious welcome.

"I am pleased that there is expressed recognition of what we have been saying in Arizona: immigration reform will not succeed unless and until we have achieved effective border security," Brewer said in a statement.

However, it met with a decidedly mixed response from other Republican leaders nationally, who said that while they supported some kind of immigration overhaul, they were unclear if this was the right one.

"My understanding is it's basically just saying that we're going to give everybody amnesty," said Steve Munisteri, chairman of the Republican Party of Texas.

"But we do need immigration reform that recognises the fact that we have a lot of people already here, that are necessary to be here, that are hard-working, law-abiding people that would add to the country," he added. "We should figure out a way for those people to have a way to stay."

Some others in the party, which lost Hispanic votes in the November election that gave President Barack Obama a second term, saw support for the measure as way of building bridges to Latinos, who are the country's fastest-growing ethnic group.

"There's no question about it. We've got to deliver a better message to Hispanics and immigrants ... a segment of people we lost badly," said Chad Connelly, chairman of the South Carolina Republican Party, adding that legislation could find support if it involved better border security and assimilation measures.

"I've heard some people say this is more like 'earnesty' than 'amnesty. 'Earnesty,' as in earning their way to citizenship," he added. – Reuters