Senate Democrats blocked a Defense Department spending bill on Thursday night, marking the third appropriations bill derailed in recent weeks.

Senators voted 50-44 on moving forward with a House-passed military spending bill, which would have been used a vehicle for the Senate's own legislation. Sixty votes were needed to move forward and formally start debate.

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Democrats objected to the legislation because of larger concerns that Republicans wouldn't hold up a two-year budget deal.

Democrats sent a letter to McConnell this week calling on him to pledge that spending bills from both the House and the Senate would follow "fair funding" and avoid controversial "poison pill" riders.

Reid pointed to the current stalemate of Zika funding, arguing that McConnell must "publicly give his word that all appropriations bills ... will comply with what we talked about."

Lawmakers are currently at a stalemate over how to fight the virus. The impasse has stalled a larger, separate veterans and military construction appropriations bill, which the Zika money is attached to.

But the Republican leader fired back, accusing Democrats of being the "the dysfunction party."

"Our Democratic friends ... prevented us from taking it up because they want us to get a guarantee from the House as to what the House result will be. That's not the way it works," McConnell said.

He added that it's "inexcusable to see Senate Democrats filibustering the defense appropriations bill, jeopardizing both our combat readiness and our national security."