The Senate refused to limit debate on overhauling immigration law as Democrats urged President Bush to rally Republicans to rescue the legislation.

The 33 votes to shut off debate were 27 short of the 60 needed by the Democratic leader, Senator Reid of Nevada, to bring to a conclusion debate on legislation to grant legal status to 12 million undocumented aliens. He said he would seek another vote later today. If it fails, “the bill’s gone,” Mr. Reid said. “What else can I do?”

Mr. Reid appealed to Mr. Bush to twist the arms of Republicans who voted against limiting debate, saying an inability to pass the legislation would produce headlines that the “president fails again.”

“This is the president’s bill. He has worked long and hard,” Mr. Reid said. “This bill that’s on the floor is not a Democratic bill, it is a bill that was worked on by Democrats and Republicans in cooperation with the president.”

Since he took office six years ago, Mr. Bush has championed an overhaul of immigration law, including a guest-worker program in the legislation to help U.S. employers fill jobs Americans won’t take. The Senate imperiled the legislation earlier yesterday when it voted 49–48 to force expiration of the guest-worker plan in five years unless Congress renews it.

No Republicans voted to limit debate, and 15 Democrats voted with the Republicans to continue debate on the measure.

“It remains my hope that we can complete this process,” Senate The Republican leader, Senator McConnell of Kentucky, told reporters after the vote. “This is all solvable in the next few days.”

Senator Kyl of Arizona, one of the chief Republican negotiators, said, “If it takes a little longer, so be it.”

The guest-worker plan is a cornerstone of the fragile agreement worked out between Democrats and Republicans, along with provisions to grant legal status to 12 million undocumented immigrants and impose tougher sanctions on employers who knowingly hire undocumented aliens.

Homeland Security Secretary Michael Chertoff, who helped negotiate the compromise for the Bush administration, said the guest-worker program is “critical” to discourage illegal border crossings.

“It’s clear that there are a lot of people trying to kill the bill,” Mr. Kyl told reporters earlier. “We need to get back on track.”

Senator Lott of Mississippi, the Senate’s no. 2 Republican and a supporter of the legislation, urged colleagues to stop trying to kill the measure and work toward a final vote because “this is one of the biggest issues facing the country.”

Mr. Lott also said yesterday that Mr. Bush should focus on the business of the G–8 summit in Europe instead of the immigration debate.

“We don’t need him,” said Mr. Lott, who criticized Mr. Bush for accusing the measure’s opponents of fear-mongering. “I don’t think his comments last week were helpful.”

Throughout a marathon session that lasted past midnight, the measure survived challenges designed to fray the compromise. That included an amendment by Senator Obama, a Democrat of Illinois, to set a five-year expiration on a new point system for picking which legal immigrants would enter America.

Mr. Obama, a candidate for the 2008 Democratic presidential nomination, called the point system a “radical shift” away from the current approach favoring family reunification. The point system would give preference to workers with specific job skills and educational credentials.

Republicans say the idea would help American companies recruit the best workforce in a competitive global economy, citing Canada and other countries as examples.

Mr. Obama said the point system would “radically change the way we judge who is worthy of lawful entry into American society” and is “premised on the view that there is something wrong with family” immigration.