The White House is close to sending a proposal to Congress that would demand strict immigration measures in exchange for helping people enrolled in Deferred Action for Childhood Arrivals (DACA).

The plan, which was drafted by senior policy adviser Steven Miller, would cut legal immigration in half over the next decade and dramatically ramp up punishments for immigrants living illegally in the U.S., according to a source familiar with the proposal.

It’s all but certain the plan would run into a wall of opposition on Capitol Hill. Democrats have roundly rejected similar legislative proposals and slashing legal immigration levels is likely to divide Republicans.

A stalemate over the plan could endanger Trump’s pursuit of a deal to benefit hundreds of thousands of young immigrants who benefit from DACA, the Obama-era initiative that allowed young undocumented immigrants to seek deportation relief and work permits.