Senate Budget Chairwoman Patty Murray wants Republicans to engage in budget negotiations to replace the sequester before the August recess, saying bipartisan talks provide the only way for the parties to agree on higher defense spending levels.

In a memo to fellow Democrats last week, the Washington senator said the “case for austerity as a fiscal policy in the United States has dissolved,” adding that if Republicans want to preserve defense spending at their preferred $552 billion level in fiscal 2014 they will have to change current law, a move that would require Democrats to agree.

“When we return in July, we will have a narrow window of opportunity to work toward a bipartisan budget deal, replace sequestration in a balanced way for this year, next year, and beyond, and prevent another round of uncertainty and brinkmanship in September,” Murray wrote.

Her effort will not be easy. Many in Washington doubt Congress will make any major budget decisions before August, because any agreement is likely to be tied to raising the debt limit, which is not expected to be necessary until October or later.

House and Senate appropriators are marking up fiscal 2014 spending bills using different overall discretionary limits, with the Senate following a top line of $1.058 trillion and the House $967 billion. Although the $967 billion matches the overall level of spending allowed under the sequester, the House budget resolution allocates $552 billion for defense spending — $54 billion more than the defense cap in the sequester permits.

This means if Congress passes appropriations bills at the House-adopted $552 billion defense level, defense spending would be subject to automatic, across-the-board-cuts — unless lawmakers also include a provision to modify the sequester. If spending bills are passed at the Senate-recommended levels, both defense and domestic spending would be subject to cuts.

At some point before the end of the fiscal year on Sept. 30, lawmakers will have to agree on fiscal 2014 spending levels — which may or may not be subject to automatic cuts, depending on whether Congress modifies the sequester included in the 2011 deficit reduction law (PL 112-25). If they don’t, a partial government shut down would ensue.

Murray has been pressing House GOP leaders to agree to go to conference on the contrasting House and Senate budget resolutions (H Con Res 25, S Con Res 8) for next year, even though many doubt that the two sides can reach a compromise.

House Budget Chairman Paul D. Ryan, R-Wis., said he won’t go to conference until he and Murray agree on a “framework” that would increase chances of success. Ryan and Murray have met several times to discuss a framework, most recently last week.

“Both sides are far apart,” Ryan spokesman Will Allison said when asked about the Ryan-Murray talks.