One reason, Senator Sessions said, is that immigrants in the military are more likely than US citizens to be spies.
He drew a hypothetical contrast between a Kenyan immigrant and a person from his own state. “I just think in terms of who’s going to be most likely to be a spy: somebody from Cullman, Alabama, or somebody from Kenya?”
President-elect Donald Trump’s choice for attorney-general suggested two years ago that Kenyans could become spies if allowed to join the US military.
Mr Jeff Sessions, a Republican senator from Alabama, told a radio interviewer in 2014 that undocumented immigrants should not be allowed to serve in the US armed forces.
Mr Trump’s announced pick for attorney-general also cited the case of a Kenyan in the US Navy who was arrested in Alabama in 2014 on charges of attempting to extort $50,000 from a local bank president.
“How did he get in the Navy?” Senator Sessions asked in regard to Mr Edwin Kigathi Gitau. Mr Gitau was acquitted in 2015.
Referring to education requirements for serving in the US military, Senator Sessions added, “I’m wondering: could you get good test scores from his high school? Could you get a good grade point average from Kenya or wherever?”
The Intercept, a US online publication, published Mr Sessions’ comments on Tuesday.
Several Kenyans are known to have served honourably in the US armed forces, including in Afghanistan.
US law permits immigrants who join the armed forces during periods of conflict to apply for naturalisation. The United States has officially been designated as being in conflict since the terrorist attacks of 2001.
Mr Sessions was taking issue with a proposal in Congress to make some undocumented immigrants eligible for military service and eventual United States citizenship.