President Donald Trump threatened Sunday to push the government into a shutdown ahead of the coming spending deadline in September if Congress does not fund his border wall and change the nation’s immigration laws.

“I would be willing to ‘shut down’ government if the Democrats do not give us the votes for Border Security, which includes the Wall! Must get rid of Lottery, Catch & Release etc. and finally go to system of Immigration based on MERIT! We need great people coming into our Country!” Trump tweeted.

Trump has previously floated the possibility of a government shutdown over border security and immigration, and on Sunday he made his threat explicit, saying he would do so unless Congress funds his proposed wall, which he promised Mexico would pay for, and puts in place his preferred immigration policies. “They don’t want the wall,” Trump said. “But we’re going to get the wall, even if we have to think about closing up the country for a while.”

A shutdown over Trump’s wall at the September deadline would mark the third lapse in appropriations this year, following a shutdown in January as Democrats battled with the Trump administration and congressional Republicans on protections for “Dreamers” as well as a brief shutdown when Republican Sen. Rand Paul of Kentucky blocked a spending vote.