President Donald Trump again signaled his support for the wall Monday, after threatening to shut down the government if Congress failed to deliver construction funding.

“We must have Border Security, get rid of Chain, Lottery, Catch & Release Sanctuary Cities – go to merit-based Immigration,” he wrote on Twitter. “Protect ICE and Law Enforcement and, of course, keep building, but much faster, THE WALL!”

On Sunday, the president said he would be willing to shut down the government if Democrats failed to support his immigration reform and border security agenda.

“I would be willing to ‘shut down’ government if the Democrats do not give us the votes for Border Security, which includes the Wall!” he wrote.

Congress faces a September 30 deadline to fund the federal government.

Trump continues to highlight tough immigration policies as members of Congress face their midterm elections in November.

He criticized House Democrats on Sunday for failing to support Immigration and Customs Enforcement (ICE) agents in a congressional vote to ban their department.

“These are brave and great men and women. They’re in the trenches every day taking the fight straight to vicious gangs. They prey on our people, they hurt our people, they kill our people,” he said in a video released by the White House. “Without the brave heroes of ICE, we would have no enforcement, no laws, no borders and therefore – we wouldn’t even have a country.”