Ten retired FBI officials and experts in counterintelligence sent a letter to Congressional leaders warning that the Biden administration's policies have facilitated a "soft invasion" of military-age men into the United States from terror-linked areas of the world.

The letter, written on Jan. 17, before Texas Gov. Greg Abbott invoked the invasion clause of the US Constitution, suggests that a terrorist attack is likely imminent.

"The threat we call out today is new and unfamiliar. In its modern history the U.S. has never suffered an invasion of the homeland, and, yet, one is unfolding now," the letter reads.

"Military age men from across the globe, many from countries or regions not friendly to the United States, are landing in waves on our soil by the thousands – not by splashing ashore from a ship or parachuting from a plane bur rather by foot across a border that has been accurately advertised around the world as largely unprotected with ready access granted."

"It would be difficult to overstate the danger represented by the presence inside our borders of what is comparatively a multi division army of young single adult males from hostile nations and regions whose background, intent, or allegiance is completely unknown. They include individuals encountered by border officials and then possibly released into the country, along with the shockingly high estimate of 'gotaways,' meaning those who have entered and evaded apprehension," the letter continues.

Sen. Ron Johnson (R-WI) called the letter "sobering."

Earlier this week, Abbott invoked Texas' right to self-defense, deeming the migrant crisis an 'invasion.' In response, a coalition of 25 Republican governors have signed a letter in support of the Texas resistance.

Meanwhile, TX Attorney General Ken Paxton posted a meme on X which reads "COME AND TAKE IT."

Of the more than 10 million illegal border crossers who have entered the US since Biden took office, more than 1.7 million are "gotaways" - those who have illegally entered and evaded capture since Biden has been in office. The majority of these are reportedly military age men.

"In light of such a daunting, unprecedented penetration by uninvited foreign actors, it is reasonable to assert that the country possesses dramatically diminished national security at this time. The nation's military and laws and other natural protective barriers that have provided traditional security in the past have been thoroughly circumvented over the past three years," the former FBI officials wrote.

The letter calls on Congress to secure the border "against these young men and those already here illegally must be identified and removed without delay."

According to the Gazette, the authors include;

Kevin Brock, former assistant director of intelligence and former principal deputy director of the National Counterterrorism Center; Chris Swecker, former assistant director of the FBI’s Criminal Investigative Division; Timothy Healy, former director of the Terrorist Screening Center; Ruben Garcia, Jr., former executive assistant director of the Criminal, Cyber, Response and Services Branch; Mark Morgan, former assistant director for training at the FBI, former acting commissioner of U.S. Customs and Border Protection and former U.S. Border Patrol chief; David Szady, former assistant director of counterintelligence; Jody Weiss, former special agent in charge in Philadelphia; David Mitchell, former special agent in charge in Milwaukee; William Gavin, former assistant director of the FBI’s Inspection Division and Timothy McNally, former assistant director of the FBI’s Los Angeles division.