President Barack Obama's bipartisan healthcare summit  "lacked diversity among participants," leaders of the Congressional Progressive Caucus charged late Thursday.

While caucus co-chairs Reps. Raul Grijalva (D-Ariz.) and Lynn Woolsey (D-Calif.) described the day's discussion at the Blair House as "important," they ultimately said it was "disappointing," as the White House did not invite any leaders from the Congressional Black Caucus, the Congressional Hispanic Caucus or the Congressional Asian Pacific American Caucus, much less any representatives from their own, progressive bloc.

"These groups reflect the significant diversity of the United States, and their participation is crucial as we debate the best way to improve our health care system," Grijalva and Woolsey stressed late Thursday in a statement.

But the two progressive leaders said they remained hopeful the primary issue they hoped to advance during the summit -- the public option -- could eventually become part of the Senate's healthcare bill.

Contrary to their own party's leaders, who have all but accepted the public option's defeat, Grijalva and Woolsey stressed there was "new momentum" building in both chambers of Congress for a government-based healthcare plan.

They consequently implored Senate Democrats to heed those calls and attempt passing a public option using the 51-vote reconciliation process.

"We believe that the public option is appropriate for a reconciliation package because it saves money and reduces the deficit," they wrote. "The money saved by implementing a public option could be used to eliminate unfair excise taxes and provide people with more assistance in paying for their coverage."

Still, the two lawmakers promised to work with their party's chiefs to advance healthcare legislation to the president's desk as soon as possible.

"Moving forward, we are determined to work with our colleagues in the House and Senate to deliver on our promise to pass health reform legislation that will provide affordable, accessible health care for every American,” they said.