Dealing a significant blow to President Bush, bipartisan efforts to move major immigration reform legislation ahead in the Senate have failed, amid disagreements between majority Democrats and Republicans over key provisions. VOA's Dan Robinson reports from Capitol Hill.

Legislation to overhaul what most assert is a broken immigration system and provide an estimated 12 million illegal immigrants a path to U.S. citizenship has been the subject of heated debate since the plan was unveiled by a bipartisan group of senators.

Supporters and the president argue that, in offering the most sweeping changes in two decades, it would mark an important step toward fixing many of the nation's immigration problems.

They assert the bill stops short of declaring an amnesty for illegal immigrants, while offering a guest worker program, steps to strengthen border security, and help immigrants, their families and American employers.

However, opponents argued against the bill on a number of fronts, with the sharpest critics saying it does amount to amnesty, and calling it flawed and lacking in sufficient enforcement measures at U.S. borders.

On Thursday, the Senate defeated repeated attempts by Democratic majority leader Harry Reid to shut down debate, which would have cleared the way for a vote.

Senator Reid warned that failure to even get the bill to a vote could end hopes for immigration reform, and be a serious defeat for the president:

"If this bill goes down with the vast majority of the Democrats voting for this action to move forward on this, and the Republicans vote against it, he and I discussed what the headline is going to be, and the headline is going to be: Democrats vote to continue the bill, Republicans vote against it, the president fails again," said Reid.

Reid said Republicans were principally to blame for blocking progress, although he noted numerous amendments from both sides of the political aisle slowed progress.

Senator John Ensign, a Nevada Republican, was among those arguing that the legislation was being pushed too fast by Democrats:

"It is too important a piece of legislation to rush it through here, to say that we want to do other things [and] we have other priorities. Well, right now I don't think the American people think that there is too much more of a priority than fixing our immigration system," he said. "It literally is broken, and we have to design an immigration system that is good for America."

Democrat Edward Kennedy made a last minute attempt to persuade fellow lawmakers to end debate and put the legislation on the path to a final vote.

"We can all find different aspects of this legislation that we differ with, but underneath it this is a proposal that is deeply rooted in remedying one of the great national challenges that we have, broken borders and broken immigration system," he said.

Senate majority leader Reid suggested Thursday that President Bush needs to become personally involved again if he is to have any chance of salvaging immigration reform.

Immigration reform also faces difficult hurdles in the House of Representatives.