KYIV - The US military has rushed its advanced anti-missile system to Israel and it is now "in place", Defense Secretary Lloyd Austin said.

THAAD, or the Terminal High Altitude Area Defense system, is a critical part of the US military's layered air defense systems and adds to Israel's anti-missile defenses.

"The THAAD system is in place," Austin said, speaking to reporters before his arrival in Ukraine on Monday.

He declined to say whether it was operational, but added: "We have the ability to put it into operation very quickly and we're on pace with our expectations."

President Joe Biden said the THAAD's deployment, along with about 100 US soldiers, was meant to help defend Israel, which has threatened to take military action against Iran in response to Teheran's missile strikes on Israel earlier this month.

Iranian Defense Minister Aziz Nasirzadeh last week shrugged off the US delivery of the THAAD system to Israel as part of the "enemy's psychological warfare".

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"The THAAD is an anti-ballistic missile system. It is not a new thing and has existed before. We assess such actions as being in line with the enemy's psychological warfare. There is no particular problem in that regard," he said.