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Senate Democrats today pushed back hard against Paul Ryan's budget, even uttering the dirty "S" word around Capitol Hill: shutdown.

"We will be moving forward with appropriations bills at the level everyone agreed to just last year," Senate Budget Chairman Sen. Kent Conrad, D-N.D., said at a news conference this morning.,  "House Republicans, I hope, will do the same. If they fail to do so, they will once again threaten to shut down the government and needlessly imperil the economic recovery."

Senate Democrats insist that Republicans adhere to spending levels agreed to in the Budget Control Act, as negotiated during the debt debate that dominated Capitol Hill late last year.  Ryan's proposal, unveiled today, lowers the discretionary spending cap from $1.047 trillion that was agreed upon in last years' Budget Control Act to $1.028 trillion for FY2013.

Republicans say that under the deal they can propose any cap under the $1.047 trillion level because that is just the top of the level. But Democrats disagree.

Senate Democrats today blasted House Republicans for what they see as "threatening to walk away from their agreements," and called on them to keep to the spending limits agreed to last year.

"This is outrageous and deeply disappointing," Sen. Patty Murray, D-Wash., said. "House Republicans are reneging on a deal their own speaker shook on less than eight months ago. They have shown that a deal with them isn't worth the paper it's printed on and they are threatening families across America yet again with the prospect of a government shutdown."

Conrad will file a budget "deeming resolution" in the Senate later today to set the spending limits for fiscal year 2013 at the levels agreed to by the Congress and President Obama last year.

"It is the law of the land, it was passed last year, it is in place," Conrad said, "Our Republican friends now seem to be walking away from these limits, even though they agreed to them just several months ago."

Senate Democrats admit there is still work to be done on a longer term plan, but with a Senate deeming resolution, Conrad says he believe the Senate will have met the budget requirements for this year.

"The Budget Control Act provided the budget for this year, for this coming fiscal year, and for the current year that we're in," Conrad said. "And I have now discharged that responsibility to the appropriators."