The U.S. Supreme Court on Monday rejected a request from a trio of conservation and environmental groups seeking to block construction of President Trump's wall along the U.S.-Mexico border.

The justices declined to consider the groups' appeal of a lower court ruling that paved the way for the federal government to begin replacing border fencing in two locations and building wall prototypes.

The judge, U.S. District Judge Gonzalo Curiel, rejected the groups’ challenge to a 1996 federal law that gives the government the power to waive environmental laws to more quickly begin work on a wall. The Department of Homeland Security sought to sidestep the laws as it pursued the projects related to construction of the border wall.

The conservation groups said the 1996 law violated the Constitution because of the power it granted the federal government.

Curiel, however, said the Trump administration did not exceed its authority when it waived environmental laws as part of its efforts to build the wall along the U.S.-Mexico border.

The Trump administration asked the justices not to hear the case.

Trump made building a wall along the southern border a key promise of his 2016 presidential campaign, during which he promised Mexico would pay for the wall. The Mexican government, however, has rejected the president’s calls for it to fund such a barrier.

Republicans and Democrats, meanwhile, have continued to spar over funding for the president’s border wall.

Trump asked lawmakers to allocate $5 billion for the wall along the U.S.-Mexico border as part of a government spending bill, and warned Thursday there was a “possible shutdown if we don’t get the wall.”

The president attacked Curiel during the 2016 presidential campaign when he oversee a class-action lawsuit against Trump University. Then-candidate Trump called Curiel a "hater" who could not be impartial because he is "Mexican."