Lawmakers involved in the negotiations to prevent a second government shutdown say they are aiming to reach an agreement on Monday night.

Sens. Patrick Leahy Patrick Joseph LeahyBattle over timing complicates Democratic shutdown strategy Hillicon Valley: Russia 'amplifying' concerns around mail-in voting to undermine election | Facebook and Twitter take steps to limit Trump remarks on voting | Facebook to block political ads ahead of election Top Democrats press Trump to sanction Russian individuals over 2020 election interference efforts MORE (D-Vt.) and Richard Shelby Richard Craig ShelbySenate GOP eyes early exit Dems discussing government funding bill into February GOP short of votes on Trump's controversial Fed pick MORE (R-Ala.), the top two members of the Senate Appropriations Committee, said a core group of four lawmakers including themselves and Reps. Nita Lowey Nita Sue LoweyTop House Democrats call for watchdog probe into Pompeo's Jerusalem speech With Biden, advocates sense momentum for lifting abortion funding ban Progressives look to flex their muscle in next Congress after primary wins MORE (D-N.Y.) and Kay Granger Norvell (Kay) Kay GrangerGOP women's group rolls out six-figure campaign for Ernst Bottom line Helping our seniors before it's too late MORE (R-Texas) would reconvene at 8 p.m. with the aim of getting a deal to break the months-long stalemate.

"I think we both agree that we can wrap this up tonight, do it tonight, not go over until tomorrow," Leahy told reporters after a core group met for a second time on Monday night.

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Shelby added that the group was currently talking about "serious, serious stuff" and that the goal was to wrap up talks and get an "agreement in principle" on Monday night.

“We’re talking about reaching an agreement on all of it," he said, adding that the odds have "improved but not crystalized."

Congress has until Friday to get a funding agreement to President Trump Donald John TrumpOmar fires back at Trump over rally remarks: 'This is my country' Pelosi: Trump hurrying to fill SCOTUS seat so he can repeal ObamaCare Trump mocks Biden appearance, mask use ahead of first debate MORE's desk if they are going to prevent the second partial shutdown in as many months.

In addition to funding roughly a quarter of the government, including the Department of Homeland Security, lawmakers need to resolve the fight over funding for the U.S.-Mexico border wall.

Leahy and Shelby were tightlipped about what had occurred during the closed-door negotiations that made them think a deal could be reached later Monday night.

But Shelby indicated to reporters after the initial closed-door meeting on Monday that they had "reopened negotiations" and were no longer "stalled."

The sign of progress is a dramatic U-turn from even earlier Monday when both sides were saying talks had been stalemated because of a snag related to Immigration and Customs Enforcement (ICE) detention beds.

Shelby said on Fox News Sunday that talks had stalemated and put the chances of getting a deal at 50-50.

Democrats have proposed a cap on the number of ICE detention beds, arguing it would force the Trump administration to focus on “serious criminals,” and that numbers were in line with those from the Obama administration.

An opening offer from Democrats late last month included funding for an average daily population of 35,520 detainees, but statutorily limited the average daily population in detention centers to 16,500 between the date of a possible deal’s enactment and the end of fiscal 2019.

But Republicans lashed out at the demand on Monday, arguing House Democrats were threatening the chances of reaching an agreement.

Majority Leader Mitch McConnell Addison (Mitch) Mitchell McConnellPelosi: Trump hurrying to fill SCOTUS seat so he can repeal ObamaCare Senate GOP aims to confirm Trump court pick by Oct. 29: report Trump argues full Supreme Court needed to settle potential election disputes MORE (R-Ky.) accused House Democrats of bending to the "radical fringe" and dropping a "poison pill" into the negotiations.

“This is a poison pill that no administration, not this one, not the previous one, should ever accept," McConnell said from the Senate floor. "Imagine the absurdity of this: House Democrats want to set a limit on how many criminal aliens our government can detain.”

— Updated at 7:14 p.m.