He made the announcement hours after the Senate Homeland Security Committee ended its hearing with Alejandro Mayorkas.
Hawley said he took issue with answers given by Mayorkas about how he will secure the U.S.-Mexico border.
“Mr. Mayorkas has not adequately explained how he will enforce federal law and secure the southern border given President-elect Biden’s promise to roll back major enforcement and security measures,” Hawley said in a statement on Tuesday.
“Just today, he declined to say he would enforce the laws Congress has already passed to secure the border wall system. Given this, I cannot consent to skip the standard vetting process and fast-track this nomination when so many questions remain unanswered,” he added.
Mayorkas previously served as the deputy secretary of DHS in the Obama administration. When he was confirmed in 2013, he did not earn any Republican votes in the Senate.
During an exchange in Tuesday’s hearing, Mayorkas was asked about whether he would use $1.4 billion in funds slated for the border wall—a chief 2015 campaign promise of President Donald Trump.
“If I may strike at the fundamental point that I believe you were inquiring of, which is will I follow the law and the execution of my responsibilities should I have the privilege of serving as the Secretary of Homeland Security. And the answer is yes I will follow the law. And what I would need to do is to understand what the law provides with respect to the obligation of funds to construct a border wall, and then see what the opportunities are to discontinue any such obligations,” Mayorkas said, per The Hill.
Trump oversaw about 450 miles of the U.S.-Mexico border wall, according to the U.S. Customs and Border Protection.
About two years ago, Trump declared a national emergency to redirect defense funds to the wall. Congress also approved the funding.
Mayorkas, in the hearing, said that the Trump plan for migrants to “remain in Mexico” would not be rescinded immediately, saying it “cannot be accomplished with just a flick of a switch.”
Mayorkas also said that “I would not abolish” the U.S. Immigration and Customs Enforcement (ICE) agency, overseen by the DHS. It came as some leftist members of Congress, including Rep. Alexandria Ocasio-Cortez (D-N.Y.), said the agency should be scuppered.