(CNN) Lawmakers return to work Tuesday facing a deadline to fund the government or risk a shutdown at the end of the month, something Republicans leaders are anxious to avoid as they brace for what could be a tough midterm election in November .

The House and Senate have made more progress this year than usual toward passing spending bills through their respective chambers. But they have yet to merge any of their separate bills into final legislation that could pass both bodies and be sent to President Donald Trump for his signature in just four weeks.

The pressure to complete that difficult task will mount in the days ahead as the October 1 fiscal year deadline approaches and Republicans, who control both chambers on the Hill, try to demonstrate to voters they can govern effectively and deserve to remain in power.

The Senate, which canceled its August recess to work on spending bills and nominations, has passed nine of its 12 appropriations bills, while the House, which took the month off, has passed just six.

"1999 was the last time the Senate passed nine appropriations bills by the end of August," said Sen. Richard Shelby, an Alabama Republican and chairman of the Appropriations Committee.

The appetite to pass appropriations bills grew after the spring, when Trump threatened to veto a must-pass spending bill that kept the government open and vowed not to sign another omnibus like it when the government ran out of money in the fall. That has motivated lawmakers to work together on issues that have easily become politicized in years past.

GOP members of the House and Senate leadership will head to the White House Wednesday to meet with the President on the path forward for the spending and appropriations bills, according to two sources with knowledge of the meeting.

Senate Majority Leader Mitch McConnell said last week that there is bipartisan desire to avoid a giant omnibus spending bill, in part, because of Trump's threat. Instead, GOP leaders have packaged the bills that fund government agencies into small groups, an effort to save floor time and pass as many bills as possible before the deadline.

"Given how completely fouled up the government funding process has been for 20 years, our Democratic colleagues in the Senate are to be commended for cooperating with us," McConnell told reporters, saying the Senate had already approved funding for 90% of the government. "It's an important step forward and ought to reassure the American public that the Congress in good hands, which we know that they'll have something to say about the first Tuesday in November."

But before McConnell can claim credit for his disciplined, regular-order approach, there are still tough hurdles ahead as the two chambers press forward with their competing bills.

In the House, where bills can pass without the support of Democrats, conservative Republicans are demanding tough policy measures related to abortion, the Affordable Care Act, immigration and other contentious issues be included in the spending measures. Conservatives like members of the House Freedom Caucus aren't expected to give up the fight easily, especially with a contentious leadership election looming after the midterms.

Rep. Jim Jordan, an Ohio Republican and a member of the House Freedom Caucus who has already announced he plans to run for speaker , tweeted before the House recess that the best way to fund the government was "to Fund the border security wall -Reduce spending outside of defense -#DefundPlannedParenthood," Jordan tweeted . "We should #DoWhatWeSaid."

In the spending bill this Fall, Congress should:



-Fund the border security wall

-Reduce spending outside of defense

-#DefundPlannedParenthood



We should #DoWhatWeSaid. https://t.co/TneUbiRUCU — Rep. Jim Jordan (@Jim_Jordan) July 30, 2018

Senators last month voted down an amendment that would have blocked federal funding from going to Planned Parenthood.

In the Senate, where 60 votes are needed for spending bills to pass, bipartisan leaders have worked tirelessly to avoid hot-button issues from torpedoing their legislation.

"The Senate will continue to move forward on appropriations bills that have bipartisan support, that are at spending levels agreed to in the bipartisan budget deal, and that reject poison pill riders and controversial authorizing language," said Sen. Patrick Leahy of Vermont, the top Democrat on the Appropriations Committee, in a statement last month

To that point, leaders are so concerned about triggering a major fight with the President over his desire for border wall funding, they are expected to put off taking up funding for the Department of Homeland Security -- as well as several other agencies -- until after the election.

Those agencies are expected to be funded on a temporary basis through a continuing resolution, or CR, until spending agreements can be reached.