Sen. James Lankford (R-Okla.) speaks as Sen. Thom Tillis (R-N.C.) listens during a news conference to announce the SUCCEED Act at the Capitol Monday. (Alex Wong/Getty Images)

An emerging list of conservative demands is threatening to derail the fledgling bipartisan effort to preserve the Obama administration program protecting from deportation 690,000 illegal immigrants brought to the United States as children.

President Trump discussed the outlines of a potential deal to protect those covered by the Deferred Action for Childhood Arrivals program with Democratic congressional leaders at a White House dinner this month. The tentative deal would couple permanent protections for those immigrants with improved border security.

But key conservative Republicans in the House and Senate are coalescing around a broader suite of policies as a condition of backing a deal, and that has Democrats and moderate Republicans warning that the current, fragile consensus could quickly break apart.

In the Senate, James Lankford (R-Okla.) and Thom Tillis (R-N.C.) introduced a conservative alternative this week to the Dream Act, a bipartisan bill that has some moderate Republican support and that Democrats want to pass as part of any deal with Trump.

The Lankford-Tillis bill, known as the Succeed Act, sets out a more onerous path to legal status for the immigrants in question, and it includes provisions barring them from taking advantage of existing laws that allow legal immigrants to petition authorities to allow foreign relatives to come to the United States.

Critics say those laws foster “chain migration,” inflating the amount of legal immigration. Eliminating the possibility of petitioning on behalf of relatives abroad is among another set of policies that House conservatives are pursuing on a separate track.

Key White House officials, including senior adviser Stephen Miller, have worked with members of the hard-right House Freedom Caucus and other Republican lawmakers to hone a list of policy demands that go beyond the border security provisions on which Democrats have signaled they are willing to negotiate.

It is unclear to what extent Trump himself will support these provisions as part of the effort to negotiate a solution for “dreamers,” as the childhood arrivals are known. But the proposals are gaining adherents among some of the president’s strongest backers in Congress.

Rep. Mark Meadows (R-N.C.), the Freedom Caucus chairman, said in an interview this week that a working list of policies that conservatives may demand includes ending the “chain migration” laws; mandating that employers use E-Verify, an online federal system to determine people’s eligibility to work in the United States; stepping up enforcement against those overstaying legitimate visas; and limiting protections for those who seek asylum at U.S. borders.

Meadows also indicated that there might be a focus on "merit-based immigration" — suggesting an effort to pursue caps on legal immigration similar to those proposed in a recent bill from Sens. Tom Cotton (R-Ark.) and David Perdue (R-Ga.). Trump has endorsed a version of the bill, known as the Raise Act.

“There’s a number of people who believe that only the more moderate members on immigration can bring anything to the table, and I think what we’re wanting to say is, ‘Listen, there are some conservative ways to deal with this,’ ” Meadows said. “We want to show that we’re willing to negotiate in good faith.”

But top Democratic aides in the House and Senate said the proposals that conservatives are seeking to put on the table fall well outside the scope of the tentative agreement that Senate Minority Leader Charles E. Schumer (D-N.Y.) and House Minority Leader Nancy Pelosi (D-Calif.) reached with Trump during a Sept. 13 White House dinner.

At the time, the two Democrats said they had agreed with Trump to "enshrine the protections of DACA into law quickly, and to work out a package of border security, excluding the wall, that's acceptable to both sides." Immigration advocates, meanwhile, are continuing to press for a bill with as few restrictions on immigrants as possible. Scores of them went to Capitol Hill Tuesday to make their case to lawmakers.

The list of issues being floated by conservatives constitutes a “complete nonstarter” that ventures far outside those parameters, a senior House Democratic aide said Tuesday, adding: “There is bipartisan opposition to many of these proposals.”

Opposition to expanding the DACA discussion outside border security measures is also sparking pushback from moderate Republicans. Rep. Mike Coffman (R-Colo.) said Monday that the deal “ought to stick to border security” while the other elements could be left to a future agreement on the status of the remaining illegal immigrants in the United States.

“We’ve got to figure out what to do with the adults who knowingly broke the law, and I think that’s where we ought to focus on interior enforcement,” he said.

The conservatives' demands, should they gain currency in the GOP's right wing, could make it difficult to reach consensus among House Republicans on a path forward. House Speaker Paul D. Ryan (R-Wis.) has indicated he will not bring any immigration bill to a vote that does not have the support of a majority of House Republicans. But he suggested this month that Trump's support would help any deal clear that hurdle.

“If we have the support of President Trump . . . that, I believe, will get a majority of our members, because our members support President Trump,” he said.

Ryan has named a working group consisting of Majority Leader Kevin McCarthy (R-Calif.) and eight other House Republicans steeped in immigration and border security issues. That group, which met for the first time Monday, includes key conservatives such as Judiciary Committee Chairman Bob Goodlatte (Va.) and Rep. Raúl R. Labrador (Idaho), a Freedom Caucus member who chairs the judiciary subcommittee on immigration.

Trump has indicated that he is eager to strike a deal and has said he would not demand that Democrats support funding for his prized southern border wall in a bill to give legal status to dreamers. But Trump had demanded significant upgrades to border security, including money for increased surveillance at the border.

Meadows, who said Monday that the list of demands remains in flux, said conservatives are also seeking to beef up the number of Immigration and Customs Enforcement agents and Justice Department immigration judges as part of any border security push. And he did not rule out that House conservatives would ultimately demand some sort of barrier.

“Even the president acknowledges that there’s a whole lot of ways that we can secure our southern border without building a physical wall,” he said. “But that’s not to suggest that there’s not a real need for a wall in some areas or even see-through fencing, and having that as part of the conservative solution is certainly on the table.”