The Senate Wednesday took up a bill to erect a fence along one-third of the U.S.-Mexico border as Republican leaders conceded that efforts to enact a comprehensive immigration reform law are dead for the year.

The fence measure was aimed at achieving at least some progress in addressing the politically potent issue of illegal immigration before Congress adjourns for the midterm elections just six weeks away.

The Senate had passed a broader bill four months ago that combined steps toward tougher border enforcement with new guest worker programs and a controversial plan to give illegal immigrants already in the United States an eventual chance at citizenship.

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But with House Republican leaders and more than half of Senate Republicans adamantly opposed to the Senate approach, Majority Leader Bill Frist ceded to reality and brought the border fence bill to the floor rather than adjourn for the year without Congress taking any steps on immigration.

"While I've made it clear that I prefer a comprehensive solution, I have always said we need an enforcement-first approach to immigration reform," said Frist. "Not enforcement only, but enforcement first."

With a 94-0 procedural vote, the Senate began its move toward the more limited approach.

The move disappointed supporters of the broader approach, including the Senate's top Democrat, Harry Reid.

"We can build the tallest fence in the world and it won't fix our broken immigration system," Reid said. "To do that we need the kind of comprehensive reform that the Senate passed earlier this year."

Reid spokesman Jim Manley said Democrats would try to force another vote on the broader Senate bill, which passed 62-36 in May, though he said Democrats expect Frist to use parliamentary tactics to block the move.

The narrower bill sets a May 2008 deadline for building the first 361 miles (581 kilometers) of fencing — along the border between California, and Arizona — and also requires 30 miles (50 kilometers) of fencing along the Laredo, Texas, border crossing.

The bill would not actually provide any funding to cover costs of the total of 700 miles (1,127 kilometers) of fencing and other barriers it would require to prevent Mexicans from entering the country illegally. According to informal estimates, the fence and other security steps could cost several billion dollars.

About $1 billion (euro790 million for the fencing is likely to be included in a bill funding the Department of Homeland Security that Congress is expected to approve for President George W. Bush before adjourning for the Nov. 7 elections.

"We cannot fumble the ball," warned Jeff Sessions. "We can't have no funding, one-third funding or one-half funding or we're not going to be able to do this job."

The now-abandoned comprehensive Senate bill would have allowed illegal immigrants in the United States more than five years to stay and earn citizenship, a provision critics dismissed as "amnesty" for illegal aliens. It would have also created a guest worker program to allow another 200,000 immigrants a year and beefed-up enforcement on businesses.