Sens. Susan Collins and Olympia Snowe said Monday that they were undecided as to whether they would support the financial regulatory conference report.

The Maine Republicans — both of whom voted for the Senate version of the Wall Street overhaul — cited a tax on banks and hedge funds inserted during conference committee negotiations as among their chief concerns.

With the death Monday of Sen. Robert Byrd (D-W.Va.) and the announced opposition of Sen. Russ Feingold (D-Wis.), Democrats can ill afford to lose the support of Collins and Snowe if they hope to pass financial reform.

“There’s much of the bill that I like and believe would strengthen our system of oversight of financial institutions,” Collins told reporters Monday evening. “But I’m not happy with the $19 billion new fee, or tax, that would be imposed that did not have consideration in the Senate.”

Snowe expressed similar concerns, and she was due to meet with Senate Banking Chairman Chris Dodd (D-Conn.) on Monday evening to discuss the conference report.

“Well, obviously I’m concerned, anytime you’re placing taxes in the legislation that was not in the Senate bill,” Snowe said. “I’m going to have a discussion with Sen. Dodd on some of these issues.”

Dodd declined to comment Monday evening on where the House-Senate compromise stood.

Collins, Snowe and GOP Sens. Scott Brown (Mass.) and Chuck Grassley (Iowa) were the only members of the minority to vote for the Senate version of the bill last month. Brown has also expressed deep reservations about the $19 billion bank tax provision and suggested he could reject the bill over it. Aides to Grassley said the Iowan was reviewing the conference report and had yet to decide whether he would support it.

Meanwhile, Sen. Ben Nelson (D-Neb.) hinted that the tax provision could be a problem for him, although he said he was still reviewing the conference report and had not drawn any conclusions.

“Anytime things happen in the conference committee, you have questions about them,” Nelson said. “And I am concerned about that. But we’re taking a look at that and are going to talk among the staff to find out what the implications are.”