"Faced with a decision about whether or not to move a bill that is bad, I won't vote to move it," Nelson told ABC News. "For sure."
Senate Majority Leader Harry Reid intends to bring his health care bill before the full Senate next week. After debating the bill, he will need all 60 Democrats in the Senate to vote for "cloture" -- in other words, to stop a Republican filibuster in order to vote on whether to approve the bill. Reid's only other option would be to resort to a process called "reconciliation," which would enable Democrats to bypass a filibuster and get the bill approved with only 51 votes.
Nelson is not the only Democrat who has threatened to vote against cloture. Sen. Joe Lieberman (I-Conn.) has said he would filibuster a bill with a government-run health insurance plan, or public option. Sen. Evan Bayh (D-Ind.) said on CBSNews.com's Washington Unplugged that he would even block a motion to proceed with debate on the bill if he strongly objected to the legislation.
Nelson said he was concerned about the proposal to create a public option. Reid is including in his bill a public option from which states could opt out.
"I have said I would look at an opt in for the states, or an option for the states to be able to create their own alternative," Nelson said.
The senator also repeated his assertion that he wants the bill to expressly prohibit the use of federal dollars for funding abortions.
When asked if he could support a bill without that specific abortion clause, he said, "I can't imagine that I would."
On Tuesday, former President Bill Clinton urged Senate Democrats to pass a health care bill, even if it is imperfect.
"What I heard him say is that you don't have to let the desire for perfection get in the way of the good," Nelson said. "And that makes a great deal of sense. But I would add the caveat that we have to be sure it is not a bad bill, that it doesn't add to the deficit, that it doesn't increase taxes, and that does, in fact, control the growth in costs."