Liberals might have received their "marching orders" from President Obama last night, but won't be open to anything less than the public option, one of their leaders said Thursday.

Rep. Lynn Woolsey (D-Calif.), the co-chairwoman of the Congressional Progressive Caucus, said that her caucus would work to define the public option in debates over healthcare reform as Congress and Obama press forward with their top legislative priority.

"Last night, we got our marching orders," she said in an interview on MSNBC. "The progressives in the House, we're ready, we're going to help define the public option so it's actually what the president want."

But she said that the caucus, comprised of the most self-identified liberals in Congress, wouldn't settle for a compromise on the public (or "government-run") option.

"The public option is the best idea, so I won't be open to any options that would weaken what the public option would bring," she said.

She maligned potential compromises as well, saying the trigger plan would get health reform "nowhere," and arguing that the idea of healthcare cooperatives are out of "never-ever land."