Sen. Heidi Heitkamp (D-N.D.) (Alex Wong/Getty Images)

A sixth Senate Democrat announced her opposition Monday to authorizing President Obama to use military force in Syria.

Sen. Heidi Heitkamp (D-N.D.) said in a statement that she will continue to listen to the case for intervention, but that she would be a "no" vote if the vote were held now.

“I still believe we need to have an open and honest discussion on the Senate floor about the potential use of force in Syria," Heitkamp said. "However, after all these meetings, I still have serious concerns. I cannot support the current Senate resolution to authorize force at this time."