Conservative Republicans in the Senate have helped deal an apparently fatal blow to President Bush's immigration bill.

Supporters have fallen 14 votes short of the 60 they needed to limit debate and clear the way for final passage of a bill that would have legalized millions of immigrants and toughened border security.

The vote was 46-to-53 in favor of limiting the debate.

Critics have blasted the plan, saying it offered amnesty to illegal immigrants.

The vote is a stinging setback for Bush, who had offered the bill as an imperfect but necessary fix of current immigration practices.

Senators in both parties say it is highly unlikely that Congress will revisit it this fall or next year.