WASHINGTON -- In a development bound to please business trade groups, senators from both sides of the aisle have voted to block new federal rules that would require employers to look harder for American workers before turning to low-wage foreign guest workers who come to the U.S. on visas.

The rules proposed by the Labor Department have strong backing from immigration and labor groups who say some U.S. employers are abusing the H-2B visa program, which is designed to let companies bring in foreign workers when they can't find enough locals for the job. Proponents of the rule changes argue that the reliance on guest workers is depressing wages in U.S. industries like forestry, seafood and construction, while also subjecting workers from Mexico and elsewhere to poor living and working conditions here in America.

But the reforms have drawn fierce opposition from business trade groups, including the U.S. Chamber of Commerce, which joined a lawsuit against the Labor Department that had managed to put the rules on hold. Opponents of the reforms argue that businesses relying on guest workers simply can't find Americans who are willing to do the job. They also say that the proposed reforms -- which would require employers to advertise more for U.S. workers, as well as foot the bill for guest workers' travel and visa expenses -- are too costly for businesses.

A Senate appropriations committee vote Thursday signaled that the Labor Department's reforms may very well die, or at least be delayed a year. Sen. Richard C. Shelby (R-Ala.) added an amendment to a labor appropriations bill that would prevent the Labor Department from moving ahead with its reforms. Although such reforms would normally have strong backing on the left -- and have a much better chance in the Senate as opposed to the GOP-controlled House -- several Democrats voted along with Republicans to successfully block them, including Sens. Barbara Mikulski (D-Md.) and Mary Landrieu (D-La.).

Both Maryland and Louisiana have significant seafood-processing industries that rely on H-2B workers.

"This is a really tough issue," Mikulski said. "Maryland is seafood, but the seafood industry has changed over the years." She noted that whereas it used to be mostly African-American women picking crabs in Maryland, it is now largely Latino women from Mexico and elsewhere who are on guest worker visas. "We want [the Labor Department] to understand the industry, the rhythms of the industry. I'm going to support Senator Shelby."

Despite her vote, Landrieu said she had concerns with the program, particularly the fact that some H-2B workers toil for around minimum wage under abusive conditions. She cited a story in The Huffington Post in which crawfish pickers at CJ's Seafood in Breaux Bridge, La., claimed they were forced to work 24-hour shifts in a locked facility under the threat of deportation. The workers sent a complaint to the Labor Department earlier this month.

"If we push back the regulation, I want my friends on the other side to know we should have some whistle-blower protections in this H-2B program," Landrieu said.

Sen. Lindsey Graham (R-S.C.) did not hold back in offering a harsher criticism of the reforms, saying that the new rules would "punish the employer." He argued that even the construction industry is having a hard time finding American workers willing to do seasonal jobs.

Still battered due to the housing crash, the construction industry's unemployment rate stood at 14.2 percent last month, the highest of any industry analyzed, according to the Bureau of Labor Statistics.

"Like it or not, there are jobs in the construction field that are going unfilled after diligent advertising and paying the prevailing wage," Graham said. "Some of these jobs for whatever reason are seasonal, too. You have the same kind of dynamic."

"Don't tell me there aren't American construction workers willing to take those jobs," said Sen. Tom Harkin (D-Iowa), who voted against the amendment. "There are."

Harkin said the guest worker reform was both an economic issue and a human rights issue, noting that some employers don't play by the rules and end up hurting their aboveboard competitors.

"Some employers would rather bring in H-2B workers on the cheap than hire American men and women," Harkin said. "It's not fair to the good businesses out there that are doing the right thing and trying to hire American workers."

Shelby's amendment to block the rules passed safely by a vote of 19 to 11 in committee, though the larger appropriations bill must still come to a vote on the Senate floor.

An industry group called the Coalition to Save America's Seafood Industry quickly praised the committee vote. "We are very pleased that committee members appreciate the danger posed by the Labor Department’s proposed rules to America’s seafood industry, which already faces so many other challenges," the group said in a statement. "We thank the senators for moving to provide time for all parties to continue seeking a more reasonable regulatory framework for the H-2B program."

The National Guestworker Alliance, an advocacy group that has pushed for reform to the H-2B program, called the committee vote "a disgrace."

"It’s a setback for guestworkers, struggling U.S. workers, and small businesses that play by the rules," the group said in a statement. "Corporations and their lobbyists have been desperate to block the Department of Labor’s new H-2B rules, because their profit model is based on exploiting guestworkers and unfairly excluding U.S. workers."