Treasury Secretary Steven Mnuchin and a senior congressional Democrat have stepped up their efforts to craft a bipartisan deal on improving the nation’s infrastructure, but both congressional lawmakers and White House officials remain skeptical that the effort will lead to a deal, according to four people familiar with internal discussions.

The talks between Mnuchin and House Ways and Means Committee Chairman Richard E. Neal (D-Mass.) have so far failed to break ground on how to pay for a package that could cost more than $1 trillion, leaving perhaps the most important roadblock to a deal in place.

Complicating matters further is that the White House has publicly thrown its support behind a bipartisan separate push in the Senate to approve a more limited infrastructure package that would fall far short of what Trump promoted as a presidential candidate in 2016.

During his campaign four years ago, Trump promised a $1 trillion infrastructure package that he said would create hundreds of thousands of jobs and rebuild roads, bridges, ports and airports, among other things. Negotiations with Congress have repeatedly faltered, though, leading critics to suspect current efforts between Mnuchin and Neal are more a political marketing ploy than an attempt to create meaningful action on the issue.

Some Congressional Democrats are doubtful the Trump administration is serious about the effort, given conservative opposition to increasing federal spending or raising taxes. And the issue is not seen as likely to go anywhere fast among West Wing officials.

Still, the revived effort demonstrates how the Trump administration and congressional Democrats are eyeing potential legislative targets after the polarizing impeachment battle is expected to end this week. A bipartisan infrastructure deal could prove a coup for the president in an election year. Some Democrats see Mnuchin as willing to negotiate, after he played a central role last year in helping cement a budget package.

“Infrastructure has been a second-tier issue, but now that Trump has got the trade deal done and the tax cut done, he will elevate it as we go into the 2020 elections,” said Stephen Moore, a Trump adviser at the Heritage Foundation, a conservative think tank.

Mnuchin has met repeatedly with Neal after the two officials worked closely together during negotiations over a revised trade agreement with Mexico and Canada, officials said. These officials spoke on the condition of anonymity to candidly discuss the private negotiations.

The House chairman has told Mnuchin he wants to be assured Trump is serious about reaching a bipartisan agreement before plowing ahead on negotiations, two officials said, given that the president angrily stormed out of a meeting with Democrats over the issue last year. House Democrats have unveiled their own $760 billion infrastructure plan but not outlined how to pay for it.

Sens. John Barrasso (R-Wyo.) and Tom Carper (D-Del.) are moving forward with a smaller bipartisan effort aimed primarily at highways and roads. Despite the talks between Mnuchin and Neal, Trump has publicly praised this deal and encouraged its passage.

“House Democrats have unveiled a principles document that appears to be an introduction of the Green New Deal 2.0 and is far from bipartisan," Judd Deere, a White House spokesman, said in a statement. "In contrast, The White House is encouraged by the bipartisan legislation moving through the Senate and believes it to be a good starting point to tackling this issue for the American people.”

The White House may include additional details about an infrastructure proposal in its annual budget to Congress when it is released in early February, although details remain unclear, one person familiar with the administration’s effort said.

The Republican-controlled Senate is widely viewed as the major roadblock to a bigger bipartisan infrastructure pact closer to what Trump promised as a candidate, with one aide for a Republican lawmaker characterizing the House plan as “dead on arrival.” There has been no serious outreach effort from the White House to Senate Republican leadership about the House effort, this person said.

GOP senators have consistently objected to any proposal that would raise the gas tax to pay for infrastructure. Some negotiators believe it would be difficult to craft a large-scale infrastructure package that does not include some type of increase in federal revenue. The U.S. government is already projected to spend $1 trillion more than it brings in through revenue in 2020, forcing the Treasury Department to add to the debt each year.

Both Trump and congressional Democrats could see political benefit by focusing on the issue, since there is widespread agreement that a major effort is needed to repair the nation’s crumbling roads, bridges and other infrastructure.

America’s infrastructure has earned a D+ grade from the American Society of Civil Engineers. That group has estimated the United States must spend $4.5 trillion by 2025 to fix the nation’s roads, bridges and other infrastructure.

Skepticism abounds in both parties that progress can be made. Previous efforts by the White House and congressional Democrats to craft an infrastructure deal have fallen apart in dramatic fashion. In April, Trump invited House Speaker Nancy Pelosi (D-Calif.) and Senate Minority Leader Charles E. Schumer (D-N.Y.) to the White House to discuss the issue, but the president abruptly left the meeting almost before it began, angered by criticism Pelosi had voiced about him earlier in the day.

The issue may present a complicated political challenge for Democrats. Most Democrats on the Ways and Means Committee are supportive of Neal’s cooperation with the White House, but some fear an agreement will give Trump a powerful talking point during his reelection bid, according to one lawmaker and one aide on the committee, who spoke on the condition of anonymity to describe the committee members’ internal thinking.

Democrats and Republicans may agree on funding infrastructure in the abstract but have divergent visions on what sorts of projects should be included in a big new federal investment, said Douglas Holtz-Eakin, a conservative economist and former director of the Congressional Budget Office.

Holtz-Eakin noted that infrastructure is managed by state governments and municipalities, which can lead to sharp partisan and regional divisions over who deserves new pots of federal funding.

“It gets hard very fast,” Holtz-Eakin said.