President Trump Donald John TrumpFederal prosecutor speaks out, says Barr 'has brought shame' on Justice Dept. Former Pence aide: White House staffers discussed Trump refusing to leave office Progressive group buys domain name of Trump's No. 1 Supreme Court pick MORE on Tuesday night vetoed a joint resolution that would overturn his emergency declaration at the southern border to aid construction of a wall, the second time he has been forced to do so.

"In short, the situation on our southern border remains a national emergency, and our Armed Forces are still needed to help confront it," Trump said in his veto message to the Senate, which the White House issued in the middle of the Democratic primary debate.

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Trump said in his message to the Senate that the national emergency has allowed the administration to "counter large-scale unlawful migration" and facilitated the construction of his long-promised border wall.

He further argued that the southern border remains a "major entry point" for criminals and illegal drugs.

Senate Majority Leader Mitch McConnell Addison (Mitch) Mitchell McConnellDemocratic senator to party: 'A little message discipline wouldn't kill us' House to vote on resolution affirming peaceful transition of power Republican lawyers brush off Trump's election comments MORE's (R-Ky.) office said the Senate would vote on Trump's veto this week, but neither the Senate nor the House is expected to have the votes to overrule Trump's veto.

The Senate and later the House voted last month to block Trump's national emergency declaration. The Senate voted 54-41 to block the national emergency, and the House voted 236-174, with 11 Republicans in each chamber voting with Democrats.

The measure was aimed at preventing the diversion of $3.6 billion for military construction projects toward the construction of Trump’s wall along the U.S.-Mexico border without congressional approval.

The vote marked the second time this year that Congress has approved legislation challenging Trump’s authority to invoke emergency powers to build his wall. The president vetoed an earlier resolution in March.

Trump has in recent weeks simultaneously insisted that the national emergency is necessary to address the situation at the border while touting progress on barriers and a steady drop in apprehensions of illegal crossings.

His administration has made cracking down on illegal and legal immigration a focal point. It also has issued a number of executive orders and new policies to pursue that agenda and urged Congress to pass stricter immigration laws.