A dispute over how many visas to issue to foreign farmworkers, and how much to pay them, looms as the chief remaining obstacle to completion of a draft bill, the focus of intense negotiations on Capitol Hill since November’s election.

Although Sen. Dianne Feinstein (D-Calif.) is not one of the eight senators drafting the overall bill, she has taken a lead in the effort to solve the farmworker issue. Negotiators for the farmworkers huddled with her Tuesday in her office while growers joined in on a conference call, the latest in a series of closed-door meetings that began in January.

In a separate meeting Tuesday, the eight senators told Sen. Patrick J. Leahy (D-Vt.), who chairs the Senate Judiciary Committee, that he should plan to convene meetings on the complex legislative package as soon as May 6, according to Senate aides. The draft already is more than 1,000 pages long.

"We’re making progress," said Sen. John McCain (R-Ariz.), one of the group of eight. "We’re trying to get it done this week."

California’s $43.5-billion agricultural business is the nation’s largest and accounts for 15% of total national receipts for crops. The state’s 80,000 farms and ranches employ more than 380,000 people, according to the California Department of Food and Agriculture.

No one in the negotiations disputes that the current farmworker system is inefficient and prone to abuse, and that small farmers and agricultural businesses need to hire foreign workers quickly and legally at competitive wages to tend fields, pick fruit, harvest crops and operate machinery.

About half of the nation’s migrant farmworkers don’t hold visas or work permits, according to the Department of Agriculture. Barely 6% are hired through the agricultural visa system, called the H-2A, because growers find the process cumbersome and unreliable.

Leaders from the United Farm Workers union, which seeks higher wages, and the American Farm Bureau Federation, which represents farmers and seeks to expand the number of visas, issued conflicting assessments as to how far apart they remain.

Labor groups want to limit the number of new workers entering the United States, and are pressing for guarantees that wages paid to foreign farmworkers would be high enough that they won’t depress wages for Americans. Growers say that if a new law significantly increases their labor costs, farmers are likely to continue to flout the law and hire workers without work permits or other legal documentation.

"If the wage is set too high, we will be in the same position we are now," said Kristi Boswell, a negotiator for the American Farm Bureau Federation. "People will not use the program."

Boswell said the two sides were "working through difficult issues. The discussion is still going on in good faith."

Advocates for farmworkers said they would hold firm for higher wages. "There aren’t too many people who believe farmworkers are paid too much for what they do," said Giev Kashkooli, a United Farm Workers vice president.

Feinstein said that the two sides had tentatively agreed on "a number of things," but that the growers had not signed off on all aspects of a deal.

"I’m very hopeful," Feinstein said. "The train is leaving the station. We need a bill, and I’ve talked to other senators, and we hope we can get [the growers’] acquiescence and support. Otherwise we just have to proceed ahead."

Feinstein has worked since January on the farmworkers issue with Sen. Marco Rubio (R-Fla.), whose state also is heavily reliant on agriculture. Sen. Michael Bennet (D-Colo.) and Sen. Orrin G. Hatch (R-Utah) joined them several weeks ago, and aides now refer to the four as the "rump group" that is focused on farmworkers.

The group has agreed to streamline the application process for farmworker visas, and to offer visas for multiple years, unlike the current H-2A visa system. The goal is to help farmers better plan their labor force as crops become ready for harvest.

In addition, the draft would allow migrants who have worked in agriculture for at least two years to apply for a "blue card" visa for themselves, a spouse and minor children. If those workers committed to work at farm jobs for at least three more years, they would be eligible to apply for lawful permanent residency and start down the path to citizenship — twice as fast as the 10-year pathway the draft bill outlines for other migrants.

Most members of Congress will turn their attention to the 2014 midterm election after the summer. That means the time to debate and pass a comprehensive package of immigration reforms is relatively limited and any delay poses potential political problems.

Senate Minority Leader Mitch McConnell (R-Ky.) said he was "optimistic" the drafters were making progress toward a bill.

"This is something that I think majorities of both sides in the Senate would like to see go forward," he said. "There is a bipartisan interest in moving this issue forward, and we’ll have to see what it looks like when we get it."

While the senators are focused on drafting the bill, both sides already are lining up for the broader debate to come. A study released Tuesday by American Action Forum, an advocacy group headed by a former economic advisor to McCain, highlighted the economic benefits of immigration reform. Conservative critics, including the influential Heritage Foundation, are preparing a report outlining what they say are the bill’s costs to taxpayers.

With Congress just back from a two-week recess, the issue will be hard to ignore Wednesday in Washington. Tens of thousands of immigration activists are expected to meet in front of the Capitol to rally for reforms, including a pathway to citizenship for the 11 million people who are believed to have overstayed their visas or to have entered the country illegally.

"There’s a lot of injustice in the fields," said Armando Lopez, who works on a lettuce and broccoli farm in Salinas, and who came to Washington to lobby. "There are bosses who don’t give workers water or don’t give breaks, but people don’t say anything because they are afraid that they will call immigration or the police."

Lopez, who was born in Mexico, entered the U.S. unlawfully in 1999 and worked on fields in Central California for 11 years before he was granted a special visa because he witnessed a crime. His flight to Washington was his first time on an airplane.

brian.bennett@latimes.com

lisa.mascaro@latimes.com