Mr. Trump was considering whether to sign the current deal, and then take either an executive action to reprogram dollars or even declare a national emergency, knowing either move would end up in court, or ask for a yearlong stopgap spending bill that might not even clear the Senate.
One person close to the president said conservatives saw the conference committee deal as a “capitulation” by the Republican leadership, one that has put Mr. Trump in a difficult spot.
A few weeks ago, in a meeting with restrictionist immigration group leaders, Mr. Trump faulted the former Speaker Paul D. Ryan for repeatedly deferring action on the wall, with promises of doing it down the road. “Now he’s out fishing!” Mr. Trump declared, according to an attendee.
Under the complex funding formula in the agreement, officials at the Department of Homeland Security, the parent department of ICE, would have “reprogramming authority” to transfer as much as $750 million from other Homeland Security programs into the detention program.
“In short, there is more than enough flexibility for ICE to respond to any forthcoming surges in illegal immigrations and apprehensions,” the document’s authors wrote.
Two Democratic aides with direct knowledge of the deal said the Republican memo was accurate in theory, but added that such a dramatic expansion in the number of beds was unlikely because it would require taking funds from other important D.H.S. programs, such as the Federal Emergency Management Agency’s disaster relief funds.
Democrats on the bipartisan conference committee hashing out a deal, under pressure from immigrant rights groups and the ascendant liberal wing of the party, stalled the talks over the weekend by demanding that any deal include a cap, at 16,500, on the number of beds dedicated to housing detainees apprehended through sweeps of communities away from the border. There are currently 20,000 such slots.