WASHINGTON — With only days left to act, federal lawmakers failed Tuesday to reach a deal on how to finish construction of a VA hospital in Aurora that has made national headlines by busting its budget by more than $1 billion.

At issue is the final $625 million the U.S. Department of Veterans Affairs says it needs to complete the facility. The VA has spent about $1 billion on the $1.675 billion project, but it needs permission from Congress to spend an additional $625 million — and soon.

If Congress doesn’t grant that permission by early October, VA officials have warned the project will run out of money and construction would grind to a halt.

As recently as last week, it appeared as if Congress would give the VA the money it needed without incident.

The Senate on Friday voted unanimously to allow the VA to spend $625 million more on the project, and Colorado lawmakers were optimistic that a months-long battle over funding was nearly complete.

But that illusion was shattered when U.S. Rep. Jeff Miller, the chair of the House veterans committee, introduced his own bill that would require the VA to pay $200 million of the extra $625 million out of a VA fund that’s used to pay employee bonuses.

Miller, a Florida Republican, has said previously that the VA needs to help pay for the mistakes at the mismanaged Aurora hospital and the $200 million would be a step in that direction.

His approach, however, could run into opposition in the Senate because some of the money from that fund is used to compensate employees who work long hours, such as doctors.

Headed into Tuesday, it was unclear which approach would have the upper hand in the House.

A vote was scheduled late Tuesday for the Senate bill, but that plan was scrapped at the last minute as lawmakers continued to fight behind the scenes.

“The stumbling block is $200 million of the $625 million and VA has yet to come up with offsets that would be acceptable,” said Miller, who added that he doesn’t want the VA to shift money away from programs such as medical services.

Asked what he expected to happen next, Miller said one possibility was that the House could take up the Senate bill and vote to amend it, a time-consuming tactic that could edge the project even closer to the funding deadline.

“All options remain on the table,” Miller said.

The uncertainty has caused no end of frustration for some Colorado lawmakers.

“This thing has had trouble on its own; we don’t have to keep adding to it,” said U.S. Rep. Ed Perlmutter, D-Arvada.

One potential solution that emerged Tuesday is that Congress could approve only part of the funding needed to complete the hospital — to the tune of $425 million.

That would keep the project going and give Congress the time it needs to come to an agreement on the remaining $200 million.

But U.S. Sen. Cory Gardner, who helped guide the Senate bill through the upper chamber, said he was skeptical of that idea.

Although the stopgap measure would stop a shutdown, it would delay a final deal between Kiewit Turner, the project’s prime contractor, and the Army Corps of Engineers, which has been asked to manage the Aurora project to its completion.

“We have put a path forward, and I hope this is the path forward that ultimately will be enacted,” said Gardner, a Colorado Republican. “We need to fund the entire project and authorize the entire project. I’m concerned the uncertainty will start to drive up costs even more.”

Caught in the middle of the funding debate are U.S. Reps. Doug Lamborn and Mike Coffman, two Colorado Republicans who sit on the House veterans committee with Miller.

Both said they want to avoid a construction shutdown, but they said they could see value in Miller’s approach.

“There is a lot of desire to fund it and put it behind us,” Lamborn said. “But I agree with chairman Miller that it has to be done in a fiscally responsible way.”

Mark K. Matthews: 202-662-8907, mmatthews@ denverpost.com or @mkmatthews