The US Senate has decided to delay voting on a controversial immigration bill that could give legal status to 12 million illegal immigrants in the US.
The immigration issue has sparked protests across the US
Last week, President George W Bush and a bipartisan group of senators crafted a compromise version of the bill that would also strengthen border controls.
Democrat leaders had hoped to pass the bill this week but the draft has sparked bitter debate.
The proposal needs to be passed by both houses of Congress to become law.
President Bush, who has made immigration reform one of his priorities, has said he wants to see new legislation in place by the end of this year.
Democrat leaders had originally intended to try to pass the bill this week but agreed to extend the deadline to June, giving more time for the proposals to be thrashed out.
"This country deserves it," Democratic Majority Leader Harry Reid said.
The Senate will now debate the bill this week and return to it after a week-long holiday.
"Our immigration system is adrift and urgently needs an overhaul from top to bottom," Democratic Senator Edward Kennedy said.
The bill's backers in the Senate are hoping they will manage to pass the bill before it gets caught up in the upcoming election cycle as politicians turn their attention to the 2008 presidential vote.
The House of Representatives is expected to try to frame its own legislation in July.
The BBC's James Coomarasamy, in Washington, says Mr Bush is likely to face quite a fight there.
The president will be able to sign the bill into law, only if the two proposals are reconciled.
Democrats argue that the bill would create "a tough but fair path to citizenship" for millions of immigrants.
Mr Reid said the agreement "can serve as a starting point" for debate but said he had serious concerns about some aspects.
Analysts say the compromise thrashed out last week has made the bill extremely complex and so open to attacks from all sides.
Under the proposed new Senate bill, illegal immigrants could seek a renewable "Z visa" after paying a $5,000 (£2,530) fine.
They could ultimately be placed on the path to permanent residency - a process that could take several years.
Heads of household would have to return to their home country first to file the visa application.
The bill also sets out a "points system" that emphasises immigrants' education, language and job skills over family connections in awarding green cards.
The bill also establishes a two-year temporary guest worker visa.
But these measures would not come into force until 18,000 new border guards are deployed, the fence with Mexico reinforced and hi-tech surveillance in place.
Homeland Security Secretary Michael Chertoff has said carrying out those provisions would take about 18 months.
Several opponents of the bill in Congress have said the proposal amounts to an "amnesty" for breaking the law.
Other critics have said the plan would limit the right of legal immigrants to be joined by their families.
Immigrants rights groups have also voiced concern at the bill, arguing the guest worker proposal will deny temporary workers the right to apply for permanent residency.