President Donald Trump's wall is no longer the biggest divide between Democrats and Republicans on immigration. The potential deal-breaker may be the status of mothers and fathers and brothers and sisters of immigrants.

Trump and Republican hard-liners in Congress are demanding that any agreement resolving the legal status of undocumented immigrants brought to the U.S. as children must end the ability of citizens to sponsor siblings, parents or adult children for a green card, which confers permanent residency and all but assures citizenship over time.

In his first State of the Union address, Trump gave only scant mention of the wall but warned of the danger posed by criminals among undocumented immigrants and those who entered the U.S. through a visa lottery system and family sponsorships.

"Under the current broken system, a single immigrant can bring in virtually unlimited numbers of distant relatives," he said, drawing some boos from Democrats in the chamber. "Under our plan, we focus on the immediate family by limiting sponsorships to spouses and minor children."

He called it "a down-the-middle compromise."

Democrats didn't see it that way.

"The White House agenda is to gut legal immigration in exchange for allowing some of the Dreamers to live here," said Rep. Luis Gutierrez, D-Ill. "For those of us who support legal immigration, and that's most Democrats and many Republicans, it won't fly."

The negotiations on immigration have overwhelmed debate on most other issues and hindered action on the federal budget and spending. After Democrats used their leverage to hold up votes in the Senate on a temporary government funding bill — triggering a three-day federal shutdown — concessions were put on the table.

While Democrats have derided Trump's demand for a wall along the U.S.-Mexico border, they've largely accepted the idea of more funding for border security — though the amount is still in question — including construction of barriers along some portion of the southern frontier. A resolution on that is likely to end in border security funding that Trump can sell to his core supporters as a down payment on a wall while Democrats tell their voters it's not a real wall.

Republican Sen. Tom Cotton of Arkansas, a Trump ally and a sponsor of legislation that would curtail legal immigration, said cutting extended-family sponsorships is "a core part" of any legalization deal. He and like-minded conservatives say immigration should be based an individual's ability to contribute to the economy.

Sen. Dick Durbin, D-Ill., said earlier this week that the limit on family migration would represent "a dramatic change" and is "one of the most serious problems in the Republican proposal."

"The strength of American families has been a pillar of our country for as long as I can remember," said Durbin. "And to limit family reunification and to literally divide families from their children is inconsistent with the values that I thought both parties embraced."

It's not clear how — or if — that political divide can be bridged.

Sen. John Cornyn, R-Texas, voiced frustration this week with the state of negotiations, tweeting: "On DACA, both parties seem to want the quid without the quo."