WASHINGTON (NEXSTAR) — Lawmakers want to know how the president came up with his latest idea to pressure Democrats on immigration. 

The president continues to demand that the U.S. ship undocumented migrants from the U.S.- Mexico border to largely democratic sanctuary cities like San Francisco and Portland.

Chair of the House Homeland Security Committee Congressman Bennie Thompson and two other committee chairs sent a letter to the White House asking for emails and documents. 

Thompson says the president himself caused the spike in asylum seekers by cutting aid to Central America.

“So now you take that investment away, so now the people in those countries have to leave because of the crime and other things,” Thompson said.

The letter says the idea is illegal and shocking. 

“If Democrats would step up and help the president fix the laws, this all could go away,” White House Press Secretary Sarah Sanders said. She says housing the migrants is expensive.

“We don’t want to put all of the burden on one or two border communities,” she said. 

When DHS Secretary Kirstjen Nielsen was forced to resign, advocacy groups said they feared the administration wanted a more extreme immigration policy.

“Given just how bad she was on immigration it’s hard to think of what exactly could be worse,”
Phil Wolgin with the Center for American Progress said.

President Trump reportedly pushed to transfer asylum seekers at least twice before but DHS Nielsen told the president no.