Folded into President Donald Trump’s budget proposal is a declaration to eliminate federal funding for public transit projects that isn’t already agreed upon, putting the D2 subway through downtown Dallas at risk of losing hundreds of millions of dollars.

The so-called D2, which would bury a light-rail extension under downtown, is one of two Dallas Area Rapid Transit projects that the agency is trying to fund, in part, with money from a $2.3 billion pool that’s doled out by the Federal Transit Administration. The other at-risk project is platform extensions for the red and blue rail lines. Morgan Lyons, a spokesman for DART, says the latter already has a grant proposal for consideration in the 2017-2018 fiscal year’s federal budget. And having current approval of that grant—the jargonized term being a “full funding grant agreement,” or an FFGA—would be key if a project wants to get federal dollars through this capital investment program. If Trump’s budget gets passed the way it is, that $2.3 billion pool dries up immediately for projects that haven’t already been OK’d by the feds.

Here’s the verbiage from the budget: “Future investments in new transit projects would be funded by the localities that use and benefit from these localized projects.”

That investment pool is made up of three different types of grant arrangements. D2 is categorized as a Core Capacity project, which means it must increase capacity by at least 10 percent and be located in a corridor that is already over capacity or will be in five years. The other two grant applications that get kneecapped are known as New Starts and Small Starts, the former of which subsidizes projects that cost more than $300 million and the latter goes toward those that fall under that amount. Yonah Freemark, a city planning PhD student and a reporter for Streets Blog USA, found more than 50 projects in cities as large as Los Angeles and as small as Gary, Indiana that were angling for a piece of that $2.3 billion via one of those three avenues. (In all, the Transportation Department’s budget drops by $2.4 billion next year, about 13 percent.)

Lyons advised all to remain calm about the platform extensions, at least.

“We have a proposed FFGA, so the platform extension project is advanced pretty far into the system,” Lyons said. “Certainly, you want to get an executed FFGA, and we’re going to keep working to get it. Now our effort is to get into the appropriation in this year’s budget.”

DART is hoping to get $51 million from the feds over two years, which would be about half of the total cost of the extensions. The Texas Department of Transportation will pick up the bill for the rest. The project would modify platforms at 28 stations along the red and blue lines, extending at-grade and below-grade platforms and adding more raised ones as well. The agency wants to begin construction by the end of the year.

D2’s funding apparatus isn’t as mature as the platform extensions. DART has vowed to seek “maximum funding” from the federal government, which it hopes to be somewhere around $650 million. The whole project will be about $1 billion. In 2015, the agency submitted a grant request and got the OK to begin the initial development phase. But that was to extend the line at-grade through downtown; only last October did the Dallas City Council recommend that DART develop an alternative plan for a subway, following a grassroots push that made a case for it to be buried amid questions about the viability of the surface level plan. Lyons wouldn’t speculate about what happens to the project if it can’t get the federal money.

“D2, the work’s going to continue on that one,” Lyons said. “Speaker Ryan said this morning in his news conference that this is just the beginning. We have been here before on presidential budgets; this is the beginning of the discussion season. We’ll start with what we’ve got.”

I’ve got a call into Councilman and Transportation Chair Lee Kleinman’s office to get the city’s feeling about all this. I’ll update when he calls back.