President Joe Biden’s nominee to lead the U.S. Department of Justice’s national security division said during a hearing Wednesday that he is “very concerned” about reports exposing flaws in FBI wiretap applications, and committed to working with Congress to explore possible fixes.

Matthew Olsen, a veteran lawyer in the intelligence community who most recently worked as a senior executive for Uber Technologies, told senators during his confirmation hearing that he would seek to “address deficiencies and improve processes” for approving Foreign Intelligence Surveillance Act applications, which allow the government to surveil people in the United States suspected of being foreign agents or having ties to terrorist organizations.