U.S. officials have expressed mounting concern over the potential for Iranian "sleeper cells" on American soil following the interception of about 1,500 Iranian nationals at the southern border during the prior administration.
The unknown number of illegal immigrants who may have entered undetected has heightened worries amid recent U.S. and Israeli strikes on Iran and fears of retaliation.
Sen. Bill Hagerty, R-Tenn., a member of the Senate Foreign Relations Committee, told the New York Post that the figures are deeply concerning because authorities "have no idea how many people got around." He noted that about half of those intercepted were released into the country pending court proceedings.
However, the documentary record is narrower than some of the rhetoric.
Reuters reported on March 2 that a Department of Homeland Security intelligence assessment said Iran and its proxies "probably" posed a persistent threat of targeted attacks in the United States, while judging a large-scale physical attack unlikely and identifying cyber retaliation as the likeliest short-term risk.
ABC News later reported that a federal alert reviewed by the network stated that encrypted transmissions believed to be of Iranian origin could be intended to activate "prepositioned sleeper assets" outside Iran, but the alert noted there was no operational threat tied to a specific location.
Iran remains designated by the U.S. as a state sponsor of terrorism, and its leadership has faced significant setbacks from airstrikes that destroyed parts of Tehran and other sites earlier this month.
Hagerty referenced data showing 1,504 Iranian nationals apprehended at the border between fiscal years 2021 and 2024, with roughly 700 released into the U.S. while awaiting immigration hearings.
A separate analysis citing Customs and Border Protection figures put encounters with Iranian nationals at about 1,650 from 2022 through 2025. Many reportedly traveled through Sao Paulo, Brazil, described as a hub for passport fraud.
President Donald Trump addressed the issue on March 11, saying a large number of people entered under previous border policies, but that authorities are monitoring most of them. "We’ve got our eye on all of them, I think," he said.
What is established by primary records is that Iranian-directed plots have reached U.S. soil before.
The Justice Department said on March 6 that a federal jury convicted Asif Merchant, whom prosecutors described as a trained Islamic Revolutionary Guard Corps operative, after he admitted the IRGC sent him to the United States to arrange political assassinations.
In a separate 2024 case, the department charged Farhad Shakeri in an alleged IRGC-directed murder-for-hire plot that prosecutors said included surveilling an Iranian dissident in New York and plotting to assassinate then-President-elect Trump.
What remains unproven in the public record is the broader claim that an active Iranian sleeper-cell network is already operating inside the United States.
Despite the lack of evidence, bipartisan voices on Capitol Hill have echoed calls for vigilance.
Sen. Ron Wyden, the Oregon Democrat who serves as vice chair of the Senate Intelligence Committee, cited "a lot of safety challenges" without elaborating on classified briefings.
Republican senators, including James Risch of Idaho and Rick Scott of Florida, stressed the need for alertness, with Scott saying, "It just takes one person."
Jim Thomas ✉
Jim Thomas is a writer based in Indiana. He holds a bachelor's degree in Political Science, a law degree from U.I.C. Law School, and has practiced law for more than 20 years.
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