Media playback is unsupported on your device Media caption Senator John McCain: "What has been created is a de facto amnesty"

A bipartisan group of US senators has unveiled a plan for sweeping reform of the immigration system this year.

The framework calls for a path to citizenship for many of the 11 million undocumented immigrants in the US, while tightening border security.

The eight senators promoted their proposals a day before President Barack Obama presents his own blueprint.

Correspondents say conservatives' hard line on immigration has become an electoral liability for Republicans.

In last November's elections, President Obama, a Democrat, won more than 70% of the Hispanic vote.

'Time is right'

Senator Charles Schumer of New York told Monday's news conference he hoped the bipartisan group's blueprint could pass the Senate by late spring or summer.

Analysis We are witnessing the rare sight of Republicans and Democrats working together, led by high-profile senators who have a geographical stake in the issue. The business community is broadly on board and the Obama White House is extremely keen - no doubt sensing a "legacy moment". It is, of course, far from a done deal. Translating principles into legislation will take time and require compromise. Beyond that, reform will be contingent on a critical mass of support from House Republicans, many of whom harbour suspicions of anything resembling an amnesty. But senior Republicans are desperate to claw back Hispanic votes after losing heavily to Mr Obama in this fast-growing segment of the electorate. For party strategists, immigration reform equals a fresh start with Latino voters. It's telling that Republican standard bearers on this issue include likely contenders for a 2016 presidential run.

But many conservative lawmakers denounce a path to legalisation for undocumented immigrants as an "amnesty" for lawbreakers.

Republican Senator John McCain of Arizona told the news conference the reform would be "very difficult, but achievable".

On the undocumented migrants, he said: "We, the American people, have been too content for too long to allow individuals to mow our lawn, serve us food, clean our homes and even watch our children while not affording them any of the benefits that make our country so great.

"I think everyone here agrees that it is not beneficial for our country to have these people here hidden in the shadows. Let's create a system to bring them forward, allow them to settle their debt to society and fulfil the necessary requirements to become law-abiding citizens of this country."

Sen McCain has previously backed a pathway to citizenship, against his party line.

The other six senators are Democrats Dick Durbin of Illinois, Robert Menendez of New Jersey and Michael Bennet of Colorado; and Republicans Marco Rubio of Florida, Lindsey Graham of South Carolina and Jeff Flake of Arizona.

Senators' immigration plan Path to citizenship for immigrants already in US illegally

Increased border security and tracking of visitor and other visas

Reducing visa backlogs and awarding resident green cards to immigrants who obtain advanced degrees in certain subjects from US universities

A verification system to prevent firms from hiring illegal immigrants

Allowing employers to hire immigrants if they cannot recruit US citizens, including an agricultural worker programme

In addition to a path to permanent residence and eventual citizenship, they call for measures to strengthen border security and to speed the path to citizenship for illegal immigrants who came to the US as children.

It will include a system to track departures from the US of visitors on tourist, student and other temporary visas.

Senator Graham said he hoped the plan would be strongly supported in the Senate - improving its chances of approval in the Republican-dominated House of Representatives.

He warned: "If for some reason we fail in our efforts to pass comprehensive immigration reform, I do believe it will be many years before anyone is willing to try and solve this problem."

US immigration reform efforts 2006: Bipartisan bill featuring enhanced border security, a guest worker programme and a path to citizenship passes the Senate with President George Bush's endorsement but dies in the Republican-led House

Bipartisan bill featuring enhanced border security, a guest worker programme and a path to citizenship passes the Senate with President George Bush's endorsement but dies in the Republican-led House 2007: A similar bill fails in the Senate after conservatives complain citizenship provisions would reward lawbreakers

A similar bill fails in the Senate after conservatives complain citizenship provisions would reward lawbreakers 2010: Senate Democrats backed by President Obama push so-called Dream Act - legislation to grant citizenship to some undocumented immigrants brought to the US as children; it dies amid Republican opposition

Senate Democrats backed by President Obama push so-called Dream Act - legislation to grant citizenship to some undocumented immigrants brought to the US as children; it dies amid Republican opposition August 2012: President Obama uses his executive authority to create a mechanism similar to the Dream Act; Republicans complain he usurped their constitutional authority

President Obama uses his executive authority to create a mechanism similar to the Dream Act; Republicans complain he usurped their constitutional authority November 2012: Hispanic voters, driven in large part by anger at the Republican opposition to immigration reform, overwhelmingly back Mr Obama and the Democrats in the election

But Republican Senate leader Mitch McConnell said any bill on the critical issue of immigration would need to be written after wider consultation.

"This effort is too important to be written in a back room and sent to the floor with a take-it-or-leave it approach," he said in a statement.

Meanwhile, Representative Lamar Smith, formerly chairman of the House Judicial Committee, said: "When you legalise those who are in the country illegally, it costs taxpayers millions of dollars, costs American workers thousands of jobs and encourages more illegal immigration."

White House press secretary Jay Carney said of the bipartisan group's proposal: "We welcome this. We think this is positive."

President Obama is to travel on Tuesday to Las Vegas, Nevada, to lay out his own immigration-reform vision, which is expected to be similar to that of the senators.