WASHINGTON, DC - JULY 15: Bob Corker (R-TN) makes his way to the Senate Chamber before a bi-partisan joint caucus. (Jahi Chikwendiu/WASHINGTON POST)

* Voting on seven Obama nominees set to begin at 11 a.m. ET

* Democrats threaten to strip Republicans of power to filibuster

By Thomas Ferraro and Richard Cowan

WASHINGTON, July 16 (Reuters) - U.S. senators scrambled on Tuesday to cut a deal to confirm seven of President Barack Obama’s executive-branch nominees and end a Democratic threat to strip Republicans of their power to block such nominations with procedural roadblocks known as filibusters.

“We are making progress,” said Republican Senator Bob Corker, one of a number of lawmakers involved in bipartisan talks over nominations that intensified in recent days.

It remained unclear if they would have an agreement by 11 a.m. ET, when the Democratic-led Senate is set to begin voting on the first of the seven nominees.

The nominations are: Richard Cordray to be director of the Consumer Financial Protection Bureau; Richard Griffin, Sharon Block and Mark Pearce to be members of the National Labor Relations Board; Fred Hochberg to be president of the U.S. Export-Import Bank; Thomas Perez to be labor secretary, and Gina McCarthy to be head of the Environmental Protection Agency.

Filibuster have long been a central tool in the Senate to permit the minority to extend debate and pressure the majority to compromise.

But in recent years, each side, when in the majority, has accused the minority of using the filibuster to create partisan gridlock rather than to find bipartisan solutions.

Democrats have accused Republicans of selectively blocking Obama nominees, not because of their qualifications but because Republicans do not like the agencies that they would head.

Reid has said that unless all seven nominees up for votes on Tuesday are confirmed, Democrats were prepared to ignite for the first time “the nuclear option,” a procedural power play that would be used to change Senate rules on filibusters.

Democrats, who control the Senate 54-46, have said their aim would be to reduce to 51 from the current 60 the number of votes needed to end filibusters against executive branch nominees.

Normally 67 votes are needed to change Senate rules, but Democrats could do it with just 51 under the nuclear option, which would involve a ruling by the Democratic chair.

Such action would cap years of Senate partisan battles and paralysis and likely trigger even more fights and gridlock between Obama’s Democrats and Republicans.

While Reid has threatened to change the rules on filibusters, he has said he wants to maintain the 60-vote threshold needed to end its use on judicial nominations and legislation.

Members of the Senate have been fighting over Obama’s nominations for years. After Reid scheduled votes on the seven nominees for Tuesday, all 100 senators met for more than three hours Monday night to again try to hash out their differences.

According to Senate aides, Republican Senate Leader Mitch McConnell offered to permit all seven nominees to be confirmed, if Reid promised in return not to try to change rules on filibusters for the rest of this Congress.

Reid countered by asking if McConnell would promise not to filibuster any more of Obama’s nominees, an aide said.

McConnell declined, prompting Reid to declare, “No deal,” the aide said.

“A lot of folks said we should avoid this, and urged the leaders to find a way,” Democratic Senator Carl Levin told a breakfast meeting of reporters on Tuesday sponsored by the Christian Science Monitor newspaper.

A Senate Democratic aide said there was the possibility that negotiations could continue throughout the day, even as votes on the nominations were being held on the Senate floor.

(Additional Reporting by Patricia Zengerle; Editing by Philip Barbara)