WASHINGTON ― If Congress wants to pass the 2020 defense policy bill before the end of the year, lawmakers may have only three weeks to break a partisan deadlock between the House and Senate.

Though armed services lawmakers initially hoped to quickly reconcile competing versions of the 2020 National Defense Authorization Act, the process has stretched on for nearly two months, in part over Democratic opposition to President Donald Trump’s diversion of military funding for his border wall.

There were signs of a thaw when House Armed Services Committee Chairman Adam Smith, D-Wash., met with officials at the White House to negotiate late last month, and on Thursday when Smith sent Senate Armed Services Committee Chairman Jim Inhofe, R-Okla., a counteroffer to an offer Inhofe made to Smith.

In recent weeks, Smith said the partisan splits were on war powers, Guantanamo Bay, transgender service members, the Feres Doctrine, the so-called widow’s tax and the border wall. Heading off Trump’s diversion of defense funding toward the U.S.-Mexico border wall has been a top priority of House Speaker Nancy Pelosi, D-Calif., who has called it an "assault on our power of the purse.”

Inhofe and his camp have been pointing to the clock for weeks, likely as part of a strategy to pressure Smith, the House’s Democratic leadership and the White House. In his messaging, Inhofe frequently noted an annual bill has passed for the last 58 years.

Senate Majority Leader Mitch McConnell, R-Ky., reportedly gave a closed-door presentation to his caucus several months ago that suggested the Senate could tackle impeachment proceedings against Trump before year’s end, if the House votes by Thanksgiving. Since then, the prospect of impeachment dominating the Senate has fueled questions about how the stalled defense policy and appropriations bills will be completed.

To add to the pressure, Inhofe last month introduced an unpopular “skinny” version of the 2020 defense policy bill as a backup plan. It would authorize only essential military construction and acquisition programs, and drop many other measures, including a new armed service focused on space — something sought by the president.

“I’ve spoken with several Democrats and Republicans, and nobody likes it, but they all agree that it has to happen if we can’t get together,” Inhofe said of his slimmed-down NDAA. “I have no doubt that is having a very positive effect on people’s anxiety to get it done.”

Not everybody agrees. Smith has spurned Inhofe’s bill, saying a bill that does not restrict the president from using defense funding for his southern border wall project would be challenging to bring to the House floor. “I am confident we can reconcile our differences and put the country first,” Smith said last month.

This week, an aide on the Republican-controlled Senate Armed Services Committee warned that it would take roughly 20 days to process the NDAA and bring it to the floor.

This would include holding “page turn” meetings, wherein both committees review the final report; getting signatures from conferees; abiding the House’s rule that requires that legislative text be made publicly available for a full 72 hours before it may be considered; as well as House and Senate floor consideration.

According to the SASC aide, if conferees reach a deal on Nov. 12, which is the Monday after the House’s Veterans Day recess, a bill could not be brought to the floor until the first week of December, at the earliest. That leaves only a few days before Congress begins its Christmas recess on Dec. 12.

“There are only 23 scheduled legislative days (including Mondays and Fridays) left in the Senate and 16 in the House — and Congress has a lot on its plate,” the aide said in an email. “The Senate’s time could be devoted entirely to impeachment in December and likely well into January, leaving no room for legislating.”

According to an aide for the Democrat-led House Armed Services Committee, Smith asked his staff to be ready to work on the bill past the start of Congress’ Christmas recess.

Despite the handwringing over the time-consuming preparations before an NDAA can pass Congress, Todd Harrison, director of budget analysis at the Center for Strategic and International Studies think tank, said the timeline can be compressed because many of the relevant rules and processes can be waived if necessary.

“But the underlying point remains the same: There are not many legislative days left in the year if their goal is to get this done before Jan. 1,” Harrison said.

It would not be unprecedented if the process dragged into the new year, as the 2008 NDAA was not signed into law until Jan. 28, 2008, and the 1996 NDAA was not signed until Feb. 10, 1996, Harrison said.

“The start of the calendar year is not a hard deadline for the NDAA to be enacted,” he added.