The Taliban, a Sunni Islamist nationalist group, recently regained control of Afghanistan after the Biden administration ordered a full withdrawal of the U.S. military from the country following 20 years of war.
"Since reestablishing control of Afghanistan, the Taliban resumed the same murderous and oppressive habits that characterized their leadership tenure prior to the arrival of U.S. forces in 2001," the senators wrote. "Even as the administration concluded the withdrawal of U.S. and allied forces from Afghanistan, we saw public attacks on individuals, beatings of women and girls, and search teams actively pursuing allies and partners."
The senators added that the most concerning aspect of the group and its control over Afghanistan "is that among those beaten and chased by Taliban forces were American citizens and their families still living in Afghanistan."
Republican Sens. Rick Scott of Florida, Dan Sullivan of Alaska and Tommy Tuberville of Alabama signed the letter.
The State Department recognizes al Qaeda — which the Taliban helped protect following the Sept. 11, 2001, terror attacks — and a number of other groups as FTOs, but the Taliban has yet to make the department's list.
The listed organizations must engage in terrorist activity that threatens the security of U.S. nationals or the country's national security, according to the State Department.
The Taliban is responsible for the most insurgent attacks in Afghanistan, according to the Director of National Intelligence (ODNI), and has denied basic health care and educational rights to Afghan citizens, especially women.
"The Taliban appointed Sirajuddin Haqqani, the leader of the Haqqani network and a known terrorist wanted by the FBI for the murder of American citizens, as Interior Minister and allowed terror organizations to join the government," the senators said.
They continued: "Given their history of supporting terror attacks on the United States, their brutal style of governance, their continued display of atrocities against Americans and our allies, and now, their enhanced military capability, the current version of the Taliban government presents a significant threat to the United States … We believe the Taliban easily meets all three criteria and urge you to consider designating the Taliban as a foreign terrorist organization and treating them as such to the maximum extent of the law."
In addition to Ernst's letter, lawmakers introduced two resolutions in the House and Senate Tuesday calling on the State Department to designate the Taliban as an FTO.
Blinken on Monday took questions from lawmakers during a House Foreign Affairs Committee hearing on the Afghanistan withdrawal. The secretary said the nature of the relationship the Taliban will have with the U.S. and rest of the world "will depend entirely on its conduct and actions" on freedom of travel, holding up human rights and counterterrorism.
He says there is "significant leverage" the world holds against the Taliban, noting that travel restrictions are in place, there are U.N. sanctions against the Taliban, and Afghanistan's financial reserves are currently frozen in banks that are almost exclusively American.
The Haqqani network, whose leader leader, Sirajuddin Haqqani, is deputy leader of the Taliban, has been designated as a FTO since 2012.
Fox News' Adam Shaw contributed to this report.