Washington DC - Iran's ballistic missile assault on Israel was "defeated and ineffective", the White House said on Tuesday, warning that Tehran could expect severe consequences for the attacks.

"Based on what we know at this point, this attack appears to have been defeated and ineffective," Jake Sullivan, US President Joe Biden's national security advisor, told reporters.

Sullivan hailed US efforts to repel some of the attacks, which involved American naval destroyers shooting down some of the missiles.

Iran's attack was, however, a "significant escalation" of tensions in the Middle East, Sullivan said – adding that it was an "ongoing situation" that meant he could only answer a few questions before getting back to his desk.

Israel-Gaza War Iran's foreign minister addresses question of US contact ahead of strike on Israel

"Obviously, this is a significant escalation by Iran, a significant event, and it is equally significant that we were able to step up with Israel," Sullivan told the briefing.

The White House official would not say what consequences Tehran could expect to face, saying it would discuss "next steps" with Israel.

"We have made clear that there will be consequences, severe consequences, for this attack, and we will work with Israel to make that the case," Sullivan said.

US Secretary of State Antony Blinken said separately that Iran's missile attack was "unacceptable" and that the entire world should condemn it.

"Initial reports suggest that Israel, with the active support of the United States and other partners, effectively defeated this attack," Blinken told reporters.