Can North Korea’s missiles deliver an atomic weapon to the U.S. mainland? Maybe.

Although recent missile tests indicate that North Korea has made advancements in missile technology, it’s unknown whether its missiles can deliver an atomic weapon to the continental United States.

“The bottom line is we don’t know,” said Ted Postol, a Massachusetts Institute of Technology professor emeritus of science, technology and international security. “I believe it’s unlikely they can deliver an atomic bomb to the United States at this time, but we can’t rule it out.”