Republican senator says Trump 'won't sign' funding agreement that includes contractor back pay Negotiations hit a new snag just two days from the government funding deadline.

With just two days left for lawmakers to reach a deal to keep the government open, negotiations hit a new snag Wednesday over a push by Democrats to include back pay for thousands of federal contractors hit by last month's longest-ever partial shutdown.

Republican Sen. Roy Blunt said President Donald Trump would refuse to sign any agreement that includes contractor back pay.

"I've been told the president won't sign that," Sen. Blunt told ABC News. "I guess federal contractors are different in his view than federal employees."

Despite the push by lawmakers to include the back pay provision for contractors, the issue has never been previously addressed in past government shutdowns.

A source familiar with the White House's stance told ABC News that such an attempt could pose a logistical nightmare, considering many contractors are paid through third-party companies, something that could increase the potential for fraud. A separate White House source confirmed that the president would likely reject the agreement if back pay is included while cautioning that negotiations between the Hill and White House were ongoing and the president could always reverse course.

"It’s projected that the federal administrative expense to implement what’s required under the bill could be as high as the actual payouts to contractors," an administration official familiar with the legislation told ABC News. "Even with detailed guidance, the risk of improper payment, overpayment, and fraud, waste and abuse is likely to be significant."

But Minnesota Democrat Sen. Tina Smith, who is leading the effort to provide back pay to contractors, tweeted that the “argument that it’d be $$$ to implement is bogus.”

Democratic Sen. Chris Van Hollen of Maryland similarly reacted to Blunt's comments with alarm.

"It would be cruel and unnecessary to block back pay for federal contract workers who lost more than a month of wages and are still behind on bills due to President Trump’s shutdown," Van Hollen said. "Many of them work low-wage jobs and live paycheck-to-paycheck."

But the issue could pose significant logistical challenges, as the government has said it doesn't know how many contract workers were affected by the shutdown and that it has no current estimate for how much it would cost to compensate those it determines are owed back pay.

The price tag for work not performed would also likely be high. According to the Congressional Budget Office, the federal government spends some $500 billion a year for contracted products and services, although that money includes federal spending not affected by the shutdown.

President Trump has continued to leave open the possibility he could still reject the bipartisan agreement, telling reporters earlier Wednesday that he and his advisers will be "looking for landmines" in the final legislative text.

Republican Sen. John Thune told reporters on Capitol Hill that there's still hope that lawmakers can find a way to "make sure federal contractors are taken care of."

“I just don’t think it’s ever been done before and figuring out duration of contracts - I mean, it sounds like it’s the timing issues. Hopefully, they’ll get it resolved,” Thune said.

Democratic lawmakers and aides said as of Wednesday afternoon that they hoped to be able to release the final legislative text of the agreement by later in the evening.