There is no one solution to strengthening U.S. borders and the issue will require further study, Alejandro Mayorkas, President-elect Joe Biden’s nominee to be the next Homeland Security Secretary said on Tuesday.

Mayorkas told the Senate Homeland Security and Governmental Affairs Committee that he hasn’t examined whether existing physical barriers along the southern U.S. border should be removed but said it’s not a “monolithic challenge” to achieving border security.

“The border is varied, depending on the geography, depending on the specific venue, and depending on the conduct of individuals around it,” Mayorkas said in response to a question by Sen. James Lankford (R-Okla.) about whether existing barriers should be dismantled. “And we don’t need, nor should we have, a monolithic answer to that varied and diverse challenge.”

The committee heard testimony from Mayorkas as part of his confirmation process.

President-elect Biden has said he won’t put additional funding toward a border security wall and Mayorkas told the panel that he will execute on Biden’s plans.

Sen. Josh Hawley (R-Mo.) noted that Congress in fiscal year 2021 provided $1.4 billion funds for additional border barriers and asked Mayorkas if he will obligate these funds as “allotted and designated by Congress.” Mayorkas replied that he will “follow the law” and that he will review his legal options for not obligating for the FY ’21 funding “and act accordingly.”

Mayorkas told the committee he is aware of the various challenges along the southern border, including illegal trafficking of aliens, contraband and drugs.

“I look forward to studying the border to make sure those challenges are repelled,” he said.

During the Obama administration, Mayorkas served first as the director of U.S. Citizenship and Immigration Services and then as deputy secretary of DHS. During those years, the administration completed installation of more than 600 miles of various physical barriers along the southern border and added new surveillance technologies.

The Trump administration put more emphasis on more robust barriers along the southern border, although Congress made sure to keep funding flowing for border security technologies as well. Spending on the physical barriers during the Trump administration far outpaced funding for border security technology.

Border Patrol agents like having the barriers in certain areas to slow entry of illegal aliens into the U.S., giving agents more time to interdict them.