A fiery dispute between Sen. Olympia Snowe (R-Maine) and Senate Majority Leader Harry Reid (D-Nev.) on Thursday threatened to scuttle a small-business research bill after four weeks on the Senate floor.

Snowe insisted on a vote on her amendment that would require reviews of the effect of new regulations on small businesses, but Reid said unnamed Democratic and Republican Senators objected to holding one.

“I am disappointed that my friend from Maine is killing this legislation,” Reid said to Snowe as she objected to a unanimous consent request to finish the small-business bill after votes on 10 additional amendments.

Snowe argued that her amendment directly speaks to the subject of the bill and that Senators can vote against it if they don’t like it.

But Reid said that the small-business bill probably would not return to the Senate floor if Snowe continues to press for a vote, because too many other national priorities must be addressed after the Senate returns May 2 from a two-week recess. He hinted that she was trying to “send a political message” by offering the amendment.

Snowe is up for re-election next year and could face a difficult challenge in a Republican primary.