President Donald Trump will not sign a bill de-facto legalizing illegal immigrants brought to the U.S. as children unless it contains provisions for a wall on the southern border, he declared in a tweet Friday.

The Democrats have been told, and fully understand, that there can be no DACA without the desperately needed WALL at the Southern Border and an END to the horrible Chain Migration & ridiculous Lottery System of Immigration etc. We must protect our Country at all cost! — Donald J. Trump (@realDonaldTrump) December 29, 2017

Trump ended the Obama-era executive action, otherwise known as DACA, in September telling Congress it had six months to codify the program into law before protections expired. Obama’s DACA program issued work permits to illegal immigrants brought to the U.S. as children and granted them certain protections from deportation. There are approximately 700,000 DACA recipients in the U.S.

Democrats have been reluctant to give any concessions whatsoever on DACA, saying the program should be passed through both chambers without any concessions on Republican immigration priorities. Trump’s tweet indicates he will not allow a “clean DACA” bill and will insist that provisions to fund his southern border wall and reform the legal immigration system must be included.

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The president named chain migration and the visa lottery system as two particular immigration priorities he wants to see ended. Chain migration allows recent immigrants to legally sponsor visas for relatives to the U.S. while the lottery system allocates visas for immigrants from underrepresented countries.

Recent New York City terrorist attackers were found to have been beneficiaries of either chain migration or the diversity visa lottery program.

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