By Kyle Trygstad

Massachusetts Sen. Scott Brown announced today he will not support the Wall Street reform conference report in its current form because of its inclusion of a bank tax. Brown announced his opposition in a letter to Sen. Chris Dodd and Rep. Barney Frank, the lead Democratic negotiators on the bill.

"I am writing you to express my strong opposition to the $19 billion bank tax that was included in the financial reform bill during the conference committee," wrote Brown. "This tax was not in the Senate version of the bill, which I supported. If the final version of this bill contains these higher taxes, I will not support it."

Brown was one of four Republicans to support the original Senate version of the bill, which passed May 20. The House-Senate conference committee concluded negotiations Friday and both chambers were expected to vote on the conference report this week, enabling President Obama to sign by July 4.

With the death of West Virginia Sen. Robert Byrd and Wisconsin Democrat Russ Feingold's announcement yesterday that he will not support the bill, Democrats are struggling to come up with the 60 votes necessary to overcome a likely GOP filibuster.

Three other Republicans -- Iowa's Chuck Grassley and Maine's Olympia Snowe and Susan Collins -- have yet to announce whether they will support the bill. And Washington Democrat Maria Cantwell remains undecided as well. For Democrats to pass the bill this week, they will need all four of their votes.

Democrats could re-open the conference committee to continue negotiations. Senate Majority Leader Harry Reid could also choose to hold off the vote until after next week's Fourth of July recess, when a replacement for Byrd can be appointed. But Democrats will still need GOP votes to pass it.

UPDATE: Dodd and Frank announced the conference committee will in fact reconvene at 5 p.m.