An embattled U.S. labor board was set to move forward with a proposed regulation that could make it easier for unions to organize, despite renewed political pressure from Congress to back down.

The National Labor Relations Board is set to vote Wednesday on advancing a proposal that would reduce the number of reasons for a company to delay employee voting on whether to form a union.

The proposal has further polarized the already tense relations on the board, with its lone Republican member, Brian Hayes, threatening to resign to stop the regulation from being made final.

Democrats and unions say the rule would streamline voting and eliminate unnecessary litigation and delay.

They argue Republicans and business interests have put up barriers to union organizing, and are out to protect companies like Target and Wal-Mart Stores where union drives have been unsuccessful.

Republicans, meanwhile, have characterized the rule as proof of a regulatory agenda that stifles job creation.

The Republican-controlled House of Representatives has tentatively scheduled a vote on Wednesday on a measure to nullify any attempt by the board to change its rules.

The labor front has become a bitter political battleground 11 months before the presidential election. Republicans are trying to fire up their conservative base by painting President Barack Obama and his appointees as loyal adherents of unions, who are crucial contributors to Democrats.

The NLRB, which was created in 1935, has been plagued by partisan bickering fueled by congressional inaction on appointments needed to permanently fill vacancies on the normally five-member panel.

The Democrat-led NLRB is bogged down, for example, in an ongoing attempt to overturn a decision by Boeing Co to build jetliners in non-union South Carolina.

There has not been much collegiality on this board since it was formed, said former NLRB Chairman Peter Schaumber, an advisor to Republican presidential candidate Mitt Romney. He served on the board from 2002 to 2010.

Schaumber called Democratic pressure to hold a vote on the organizing rules a hardball practice to essentially eliminate an employer's ability to express a view on unionization.

Teamsters President James Hoffa told Reuters in a statement that the current union election system can easily be abused by corporations that delay votes and retaliate against workers.

This is a common-sense rule that makes sure workers have the basic right to vote for or against a union, Hoffa said.

PUBLIC DISAGREEMENT

Usually closed-door disagreements spilled out publicly earlier this month when Hayes suggested the two Democratic members were planning to secretly move to finalize the rule on speedy union voting before their authority to do so expired at year's end.

Hayes said in a November 18 letter to the Republican chairman of the House Committee on Education and the Workforce that he would not be allowed a chance to review the rule and draft a dissent if Democrats pursued a year-end target.

He referred to the rulemaking process as opaque, exclusionary, and adversarial. He threatened to resign to stop the regulation from being made final.

At least three NLRB members are required to finalize a rule.

There was no clear sign Hayes will step down before Wednesday's vote on whether the board should proceed to draft a final rule.

The year-end deadline is of concern to Democrats because the appointment of Democratic board member Craig Becker expires December 31.

NLRB Chairman Mark Pearce fired off a November 21 response letter to Hayes, calling his comments inaccurate and misleading.

He said Hayes had been briefed at each stage of the process, and offered no revisions or made any attempt to engage colleagues about the substance of the proposals.

Neither Hayes nor Pearce were available for interviews.

Separately, Congress looks ready to jump in with a possible House vote on Wednesday.

The measure sponsored by Health Education and Workforce Committee Chairman John Kline would require 35 days between a proposed election and the vote.

The average now is 38 days and Kline's committee charges the NLRB proposals could give workers as little as 10 days to consider the consequences of joining a union.

The Obama board is determined to finalize a flawed ambush election scheme, regardless of the damage it will cause for the workforce and the board's integrity, Kline said in a statement to Reuters.

A similar proposal is before the Senate, but that chamber is run by Democrats and is unlikely to challenge the NLRB.

(Reporting by John Crawley; Additional reporting by Aruna Viswanatha; Editing by Tim Dobbyn)