The deployment of the Terminal High Altitude Area Defense (THAAD) system comes as Israel prepares to hit back against Iran for a major ballistic missile attack earlier this month, the second time Tehran directly targeted its arch foe this year.

"That system is in place," Austin told journalists, according to a transcript of his remarks released Monday.

"We're not going to talk about... whether it's operational or not, but we have the ability to put it into operation very quickly," he added.

The Pentagon announced on October 13 that it would deploy a THAAD battery to Israel. Spokesman Major General Pat Ryder said last week that an advance team of US personnel and components for the battery had arrived, with more to follow soon.

The deployment "underscores the United States' commitment to the defense of Israel and to defend Americans in Israel from any ballistic missile attacks by Iran," Ryder said.

Iran has carried out two major attacks against Israel in 2024 -- one in April after a strike on its consulate in Damascus that was blamed on Israel, and another in October that Tehran said was in response to the assassination of leaders of groups it backs in the Middle East.

US ships and warplanes have helped defend Israel from the Iranian attacks, but the deployment of the THAAD battery puts the US troops who will operate it -- as well as the highly costly system itself -- on the ground in Israel and more directly in harm's way.

The THAAD system -- which was developed in the 1990s, with the first battery activated in 2008 -- is operated by 95 soldiers and consists of six truck-mounted launchers with eight interceptors each, a radar, and a fire control component, according to the US Congressional Research Service.