"That's a no," Webb told Reuters when asked his position.

Webb's opposition to the extension makes it harder for Senate Majority Leader Harry ReidHarry ReidConservative Senate candidate calls on GOP to end filibuster Ex-Reid aide: McConnell's 'original sin' was casting ObamaCare as 'partisan, socialist takeover' GOP faces growing demographic nightmare in West MORE (D-Nev.) to pass Obama's plan. Republicans want to extend all the Bush-era rates, and on Wednesday, Senate Minority Leader Mitch McConnellMitch McConnellDems don’t want to help GOP improve repeal bill Bipartisan group of governors call on GOP to reject skinny repeal Dems get CBO scores on what they think skinny bill will look like MORE (R-Ky.) blocked a unanimous consent request to bring up a vote on Obama's plan and the GOP plan.

McConnell said that since the Democrats' preferred plan had not been put in paper form, he could not agree to schedule a vote.

"So we'd be happy to set up a vote on this issue ... just as soon as the majority leader produces a bill to show us what tax increases they have in mind. I want to make sure everyone understands the differences in our positions here," McConnell said Wednesday.

Earlier on Wednesday, McConnell tried to bring up the competing proposals in the chamber as part of a small-business bill. Reid rejected the proposal, saying they would get to the differing rate extensions soon after dealing with the small business bill.

"When I came here this morning, I repeat for the third time, I asked what business was before this body. Small-business jobs bill," Reid said Wednesday. "There has been a direct attack on that legislation by saying, 'Let’s do something else. Let’s not do this right now.' "