Updated at 3:49 p.m. ET

President-elect Joe Biden's nominee to head the Department of Homeland Security, Alejandro Mayorkas, appeared before a Senate panel Tuesday to begin his confirmation process, vowing to do everything he can so that an attack on the Capitol like the one on Jan. 6 "will not happen again."

Mayorkas, who would be the first Latino and first immigrant to lead that department, was previously the head of U.S. Citizenship and Immigration Services, a DHS agency, during the Obama administration. He then served as deputy secretary of DHS.

Mayorkas also faced questions on immigration and the border wall, cybersecurity and his prior actions as head of USCIS.

In announcing his nominee in November, Biden said Mayorkas "will play a critical role in fixing our broken immigration system and understands that living up to our values and protecting our nation's security aren't mutually exclusive — and under his leadership, they'll go hand-in-hand."

Biden has pushed for swift confirmation of his nominees. He is on pace to have few, if any, Cabinet members confirmed on Inauguration Day.

After the deadly insurrection at the U.S. Capitol on Jan. 6, however, there's been increased pressure to get national security officials confirmed quickly to prevent any gap during the transfer of power.

In his opening statement Tuesday, Mayorkas called the events of Jan. 6 "horrifying" and said that if confirmed, he will do "everything I can to ensure that the tragic loss of life, the assault on law enforcement, the desecration of the building that stands as one of the three pillars of our democracy, and the terror felt by you, your colleagues, staff, and everyone present, will not happen again."

On immigration, senators asked Mayorkas if he believed the border wall constructed by the Trump administration should be taken down. Mayorkas said that he agreed with the late Sen. John McCain, whom he called "an American hero," that the border is not a "monolithic challenge."

Mayorkas said the border "is varied, depending on the geography, depending on the specific venue, and depending on the conduct of individuals around it." He said that "we don't need nor should we have a monolithic answer to that varied and diverse challenge."

And he said he would be studying the legal authority the incoming administration has to end construction of the barrier wall, something the president-elect has pledged to do, and which Mayorkas said he would implement.

Mayorkas was also pressed on what he would do if confirmed about a caravan of Honduran refugees now said to be headed toward the southern border. He said the Biden administration would be committed to following asylum laws and that if the refugees were found to qualify "under the law to remain in the United States, then we will apply the law accordingly. If they do not qualify to remain in the United States," Mayorkas said, "then they won't."

Mayorkas said he did not support defunding Immigration and Customs Enforcement, ICE, as some progressive Democrats have called for.

He said he also supported a comprehensive immigration reform plan that President-elect Biden is expected to announce soon after he's inaugurated and said the U.S. has to focus more resources toward providing economic assistance to countries such as Honduras, Guatemala and El Salvador.

Asked about the cybersecurity challenge facing the U.S., Mayorkas told senators that "the cybersecurity of our nation will be one of my highest priorities," adding that he concurs that "the threat is real and the threat is every day, and we have to do a much better job than we are doing now."

Several Republicans on the committee called on Mayorkas to explain his actions as USCIS chief, after in inspector general's report found he intervened to help prominent Democrats, including then-Senate Minority Leader Harry Reid and Secretary of State Hillary Clinton's brother, with a visa program.

"These weren't the only three cases I was involved in," Mayorkas said. "There were dozens and dozens, whether they involved the rich or the poor, the enfranchised or disenfranchised. I became involved to be sure that our agency improved each day, that I learned of the problems we were confronted with and that I did everything to fix them."

Most senators, however, seemed to have a favorable view of the nominee — several on both sides of the aisle telling him they looked forward to working with him in the new administration.

But the prospects for a quick confirmation for Mayorkas disappeared when after the hearing, Sen. Josh Hawley, R-Mo., said he would object to fast-tracking the nomination because of Biden's immigration proposal.

Biden's nominee for secretary of defense, retired Army Gen. Lloyd Austin, and others in his security team also have Senate hearings Tuesday.

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