Secretary of Homeland Security Kirstjen Nielsen testified Tuesday that 3 in 4 individuals convicted of international terrorism-related charges in U.S. federal courts over the past 15 years were foreign-born.

"According to a list maintained by the Department of Justice’s National Security Division, at least 549 individuals were convicted of international terrorism-related charges in U.S. federal courts between Sept. 11, 2001, and Dec. 31, 2016. Of the 549 individuals, 402 were foreign-born — that’s 73 percent," Nielsen told the Senate Judiciary Committee in her opening statement Tuesday morning.

Nielsen, who took over for acting Secretary Elaine Duke in early December, said that figure does not include those convicted of domestic terrorism charges, those convicted in state courts, or others with pending charges. Instead, it mostly covers people arrested during the War on Terror, which includes wars in Iraq, Afghanistan, and multiple other points around the globe.

"This report is likely just the tip of the iceberg," Nielsen warned.

The findings come from "Protecting the Nation from Foreign Terrorist Entry into the United States," which was mandated by President Trump's Executive Order 13780.

The new report also concludes the Department of Homeland Security encountered 2,554 individuals on the terrorist watch list who attempted to travel to the U.S. in fiscal year 2017.

"That equates to seven terrorists a day. Fifty a week. The vast majority — 2,170 — were attempting to enter by air, but 335 were attempting to cross a land border, and 49 were attempting to enter by sea," Nielsen added.