Leading members of the Black Caucus are threatening to bring down healthcare reform if it does not include a strong public option.

Rep. John Conyers (D-Mich.) said that President Obama will not be able to muscle through a bill that sidesteps a government-run plan.

"[Obama] can't get 218 without a public option," Conyers said on MSNBC last night. "This is simple arithmetic."

Conyers tallied up the progressive members he expects to join him in opposing a plan with no public option.

"There are 83 Progressive Caucus members, 42 Black Caucus members 25 Hispanic Caucus members, 14 Asian Pacific members, and most of them are public option people," Conyers said.

Rep. Maxine Waters (D-Calif.) agreed with Conyers's ominous analysis and warned that House liberals will not settle for the kind of compromise that might be necessary in the Senate.

"You're asking whether or not we will support some other altnerative to public option, and I want to be very, very clear," she told MSNBC's Ed Schultz.

"We've got to have a public option. I will not vote for anything that doesn't have a public option."

At a press conference today on Capitol Hill, Congressional Black Caucus Chairwoman Barbara Lee said there was no room for debate on the issue.

"As members of the Congressional Black Caucus, we are unwavering in our support of a robust public option," she said, according to First Read.

Obama is expected to push for the public option in his address to Congress tonight, but will likely not "draw a line in the sand" by threatening to kill any reform package that lacks such a plan.