US Secretary of Defense Lloyd Austin announced on Monday that the Terminal High Altitude Area Defense (THAAD) missile defense system is "in place" in Israel.
Reuters quoted Austin telling the press that "the THAAD system is in place."
He refused to say whether the system was operational, but noted: "We have the ability to put it into operation very quickly and we're on pace with our expectations."
Asked about Israel's planned response to Iran's missile attack on the country at the beginning of the month, Austin said, "It's hard to say exactly what that strike will look like.
"At the end of the day, that's an Israeli decision, and whether or not the Israelis believe it's proportional and how the Iranians perceive it, I mean those may be two different things."
He added: "We're going to do - continue to do - everything we can ... to dial down the tensions and hopefully get both parties to begin to de-escalate. So, we'll see what happens."