Rep. Ilhan Omar, a former Somali refugee and a Democratic congresswoman from Minnesota, said racism, not an emergency, is behind President Trump’s desire build a wall at the southern border.

“This is a fake emergency! Donald Trump is lying about the border in order to build his monument to racism,” Omar tweeted Wednesday.

Omar was responding to a tweet from Trump where he threatened to close the southern border with Mexico if more is not done to curb illegal immigration from South and Central America.

“Congress must get together and immediately eliminate the loopholes at the Border! If no action, Border, or large sections of Border, will close. This is a National Emergency!,” the president tweeted.

Trump said on Tuesday that he would be looking into closing the southern border if he cannot get a comprehensive immigration reform package that includes full funding for the wall through Congress. “Mexico is now stopping people coming in … let’s see if they keep it up,” Trump said. “If they don’t or if we don’t make a deal with Congress, the border’s going to be closed. A hundred percent.”

Trump declared a national emergency at the border in February after Congress neglected to grant him his requested funding for a border wall. The executive order allowed the White House to shift executive funds from other agencies into the construction of the wall and is being challenged in the courts by 16 states.