The US Senate voted down a bill to change immigration laws late on Thursday, dealing a severe blow to the hopes of President Bush to reform the existing system before he leaves office next year.
Several amendments passed on the Senate floor before the final vote upset the fragile bipartisan majority backing the bill, which failed after only 45 senators voted in favour, when 60 votes were needed.
The bill's main objectives were to tighten border controls, but at the same time instituting a legalisation scheme for the existing illegal immigrants, whose number is thought to top 12 million.
The Republican senators favoured even stricter controls on immigration, as well as emphasizing job skills and education over family ties in awarding citizenship, a measure opposed by the Democrats, who fear that it would be detrimental to millions of families.
Bush made immigration reform one of the top issues of his agenda for the remained of this term, which expires at the end of 2008, but with the Senate split almost evenly between the Republicans and Democrats, he could find it hard to gather enough support for his initiatives.
With Bush failing to make any headway on the issue, immigration reform is set to be one of the major issues of next year's presidential campaign in the US.