President Donald Trump on Tuesday made an already difficult task even more challenging for lawmakers by calling on Congress to ratify his Mexico-Canada trade deal before passing any bipartisan infrastructure bill.

The demand, which Trump laid out in a letter to House Speaker Nancy Pelosi (D-Calif.) and Senate Minority Leader Chuck Schumer (D-N.Y.) ahead of their meeting on infrastructure scheduled for Wednesday, effectively decreases the already slim odds that a package overhauling the nation’s crumbling roads, bridges and waterways ― an issue Trump vowed to tackle during the 2016 presidential election ― will make it to the president’s desk this Congress.

Tying infrastructure to trade, an already contentious issue, is likely to further complicate matters for everyone. Although both Democrats and the Trump administration have claimed they’re making progress on reaching a deal regarding the agreement, known as USMCA, the two sides are said to still be far apart.

Pelosi, for example, wants the Trump administration to reopen negotiations with Mexico and Canada to toughen enforcement and language on labor and environmental protections. Trump officials, meanwhile, are demanding the House take up the agreement as it stands after 13 months of negotiations with Mexico and Canada.

Pelosi and Schumer responded Tuesday with a statement that did not address the president’s demand that they tackle the trade deal before turning to infrastructure.

“In our conversations with the President, Democrats will continue to insist on our principles: that any plan we support be big, bold and bipartisan; that it be comprehensive, future-focused, green and resilient; and that it be a jobs and ownership-boost with strong Buy America, labor, and women, veteran and minority-owned business protections,” they wrote.

Trump also said in his letter that Democrats should come to their meeting at the White House armed with a list of infrastructure priorities and how much funding they’d like to devote to each.

But the biggest sticking point has never been where to invest funds ― rather, it has been how to pay them. Both sides agreed during a meeting last month to pursue a $2 trillion infrastructure package, but congressional Republicans maintain it ought to be deficit neutral while also opposing new sources of revenue like a hike in the federal gas tax, which hasn’t been raised since 1993.

The sides also disagree on how an infrastructure overhaul should move through Congress. In his letter, Trump suggested using next year’s expected surface-transportation reauthorization bill as the main legislative vehicle instead of a broader infrastructure proposal. The current five-year transportation law expires in 2020, and Congress must reauthorize it in order to keep the Highway Trust Fund solvent.

“There is no doubt that the American people want us to rebuild our infrastructure to improve the quality of life for all Americans,” Trump said. “It is now time for us to follow the wishes of the American people and work together to pass a big and bold infrastructure bill.”

Democrats had made demands of their own on infrastructure even before receiving Trump’s letter ― demands the president probably won’t ever agree to, such as clean energy and labor protections. Schumer said during an interview with MSNBC earlier this month that he believed it was “unlikely” that Trump would agree.

“Then the American people will see on infrastructure, like on so much else, he’s a fraud,” Schumer said.