Washington (CNN) The Trump administration dropped a potential bomb into negotiations on the future of the Deferred Action for Childhood Arrivals policy on Sunday night -- but key players on the Hill still aren't sure yet whether the fuse is actually lit.

Reaction to the administration's priorities list of tough border security and immigration enforcement measures ranged from dismissal as "noise," to skepticism about the President's commitment level, to declarations of it being a "nonstarter" by Democrats.

Ultimately, most agree, President Donald Trump himself will have to say what his red lines are.

The White House late Sunday released a wish list of items for any potential deal to preserve DACA -- the Obama administration policy that protects young undocumented immigrants brought to the US as children from deportation. Those measures include provisions to make it harder for unaccompanied minors to enter the country illegally, money for the President's border wall and cuts to legal immigration.

But the administration is already sending mixed messages about how intensely it is getting behind the list of priorities, which were developed in part by Stephen Miller, a White House policy adviser and longtime immigration hardliner.

An administration source told CNN that it was too early to tell whether the priorities are a firm line in the sand, saying there remains a "White House divided" on the issue -- but emphasizing Trump "still wants to cut a deal."

On a call with reporters on Sunday night, a senior administration official declined to say whether the list should be read as a veto threat.

"We're not discussing what's a veto threat right now, or we're not looking to negotiate with ourselves," the official said, adding the priorities are "all important."

On Capitol Hill, most players are taking a wait-and-see approach.

House Speaker Paul Ryan's office was noncommittal. "The House immigration working group will review these principles and continue to consult with our conference and the administration to find a solution," spokesman Doug Andres said.

Other sources pointed to the timing of the release -- the Sunday night before a federal holiday -- as a possible indication the White House is not as serious about the list.

"Like they're trying to bury it," one congressional aide said. Administration sources, for their part, said the list had been in the works for some time and was simply ready to be released.

A Republican consultant familiar with the discussions on the Hill about DACA downplayed the release altogether as "noise" -- saying not much matters until the date draws nearer to December 8, when government funding runs out and any potential shutdown talk could get serious if progress hasn't been made.

"I just don't take this as that serious a proposal," the consultant said. "One given what's in there, that it's everything under the sun. And two, when they released it."

At the same time, one senior Democratic aide called it "most disheartening" that in the letter Trump sent to congressional Democratic leadership, he said the list "must" be passed.

Miller's involvement has been a source of frustration for some negotiators on both sides of the aisle who have perceived him as trying to scuttle talks.

"This isn't an opening bid that anyone's going to respond to," said Jeremy Robbins, executive director of New American Economy, a nonpartisan group, business-linked group backed by former Mayor Mike Bloomberg that advocates for moderate immigration policies. "There's just this laundry list of deal breakers, each one of which is a poison pill in its own right. ... But that doesn't change the fact that the President, if he wants to protect Dreamers and get some border security, he can do that today."

Hill work continues

Sources familiar with negotiations in Congress say they have been progressing slowly.

According to multiple sources familiar, the working group organized by Ryan, which includes key Republicans on different sides of the ideological spectrum, has met at least four times. The bare bones of a deal have yet to take shape, the sources said.

Further details remain on close hold. Members and their staffs have agreed to maintain silence on the substance of the discussions to avoid negotiations leaking to the press.

On the Senate side, sources familiar say conversations are happening, mostly among staff, but the process is less formal than on the House side.

Democrats maintain substantial leverage in the negotiations. Not only would any immigration deal require Democratic votes to pass -- both to clear the 60-vote filibuster threshold in the Senate and to make up for Republican holdouts who would never support a DACA fix -- but Democrats are already signaling they could withhold support for must-pass bills like government funding if progress isn't made.

"That is definitely on the table, and we are working to make sure that it's not just a Hispanic Caucus effort, but it's the entire Democratic caucus," said Congressional Hispanic Caucus Chairwoman Michelle Lujan Grisham in a CHC call with reporters on Monday. "If we can't get movement on a productive strategy that gives us a vote -- and we're open to considering reasonable, effective border security issues -- then yes, ... we're going to use every leverage point at our disposal."

A deal is still attainable, added Vice Chairman Joaquin Castro, but only if the White House is "reasonable."

"This was a long laundry list of hardline immigration policies including things that we've specifically said our members cannot support, including a wall," Castro said. "So we're looking for a serious proposal from the President. This is not serious. ... I would suggest the President look at this list more himself, get more personally involved, rather than assign it to a 30-year-old hardline zealot," he added, referring to Miller.