WASHINGTON — After a week-long debate, the Senate is poised to approve a spending bill that will fund agencies until the end of the fiscal year, avoiding a government shutdown at the end of March. The bill should be the final chapter on the spending debacle for the 2013 fiscal year after agencies operated for months under a temporary, continuing resolution passed last October.

Appropriations Committee Chairwoman Barbara Mikulski, D-Md., and top Republican Richard Shelby of Alabama, have pushed for passage of a continuing resolution that the House passed earlier this month. Their teamwork offers a rare moment of bipartisan compromise, set against a divided Congress that is also considering two starkly different budget bills for fiscal year 2014.

“We’re reaching across the aisle,” Mikulski said, bidding for Republican support. “We’re reaching across the Dome. That’s how we’re trying to do it.”

In a 63-35 vote Monday, the Senate agreed to end debate on Mikulski’s version of the stopgap spending bill, paving the way for final approval. If adopted by the Senate, the modified bill goes back to the House for final passage. (Update: On Thursday, following Senate passage, the House agreed to the resolution and forwarded the spending bill to President Obama.)

“If we do not pass our bill … we could face a government shutdown,” Mikulski said on the floor last week. “We are absolutely committed to no shutdown, no showdown, no lockdown, no slamdown. We want to do the job.”

The House bill renewed a continuing resolution until Sept. 30, the end of the current fiscal year as measured by the federal government. It updated the budgets for defense, military construction and veterans affairs, providing more flexibility for the Pentagon in handling the brunt of the sequester cuts. The Senate bill added three other agencies that will also get revised 2013 budgets. As it stands, all other agencies will continue operating at levels set last year, while also dealing with the pinch from the sequester.

“The legislation will avoid a government shutdown on March 27, prioritize DoD and Veterans programs and allow the Pentagon some leeway to do its best with the funding it has,” House Appropriations Chairman Hal Rogers, R-Ky., said.

Most Democrats voted against the bill in the House, including Appropriations Committee ranking member Nita Lowey, D-N.Y., who said she opposed the measure because it did nothing for the other federal agencies and departments.

“It is unacceptable that federal agencies and departments covered by the 10 remaining bills would be forced to operate under full-year continuing resolutions based on plans and spending levels enacted 15 to 18 months ago,” Lowey said.

Minority Whip Steny Hoyer, D-Md., said before the vote that the continuing resolution adopts the sequester, which is an “irrational policy.”

“Nobody expected sequestration to go into effect,” said Hoyer, who voted against the so-called CR bill. “At some point in time, we have to say enough is enough and try to get closure on these manufactured crises and have some longer term confidence-building policies in place that are rational.”

“Continuing resolutions” have become the norm in Congress in lieu of a full appropriations bill. A one-year spending package, funding all federal agencies, has won approval in both chambers in a timely fashion only three times in the last 30 years. Lawmakers have opted instead for quick fixes and delaying deadlines on big agreements.

But quick fixes come at a cost. According to a March 13 Government Accountability Office report , the practice of utilizing continuing resolutions as a substitute for a complete spending authorization has taken a toll on government agencies.

“Because CRs only provide funding until agreement is reached on final appropriations, they create uncertainty for agencies about both when they will receive their final appropriation and what level of funding ultimately will be available,” according to the GAO report. “After operating under CRs for a prolonged time, agencies faced additional challenges executing their final budget as they rushed to spend funds in a compressed timeframe.”

Last year, Congress opted to extend the appropriations deadline to March of this year and approve a continuing resolution instead, knowing that compromise would be difficult with a national  election looming.

“We were going into the heat and passion and prickliness of an election year (last October),” Mikulski said. “It was the wise head to extend it where cooler heads would prevail into March. Well, here we are. We’re the cooler heads and we’re ready to prevail.”

Mikulski said she and Shelby have been working on identifying other agencies to add to the spending called for  in the House bill.  They settled on including spending for  Agriculture, Homeland Security, and Commerce, Justice and Science.

Mikulski and Shelby’s additions include funding for food safety inspections, clean water programs under the Agriculture Department, cybersecurity and the National Science Foundation.

Other senators brought amendments to the floor last week, but most were struck down. Sens. Ted Cruz, R-Texas, and Marco Rubio, R-Fla., proposed an amendment to remove funding for the health care reform law, which failed though Republicans backed it unanimously.

Partisan proposals aside, Mikulski said she and Shelby have been seeking  common ground so the Senate legislation  can pass through the House quickly.

“In today’s toxic environment in Washington, I must say our conversations have been characterized by civility, collegiality and absolute candor,” Mikulski said. “We had to look at not what we would like to do and not even what we should do, but what we must do to keep the government operating in order to achieve the national goals that America wants.”

That candor and civility could very well end after the continuing resolution, as both chambers move to consider proposed budgets for 2014. Sen. Patty Murray, D-Wash., and Rep. Paul Ryan, R-Wis., have unveiled starkly different budget proposals for the next fiscal year , which could foreshadow yet another continuing resolution in the fall.