JERUSALEM -- Israeli military spokesman Daniel Hagari said on Tuesday that intelligence information shared by the United States indicated an imminent missile attack from Iran.

In a news briefing, Hagari said Israel was in a state of "maximal preparedness" and preparing for the possible attack with the aid of American forces in the region. He added warplanes were patrolling the skies above Israel, ready to thwart aerial threats.

According to Hagari, intelligence collected by the United States indicated that Iran is ready to launch a ballistic missile attack against Israel within a short time. He added, however, that no launch from Iran has been detected so far.

"Iranian fire on Israel will bring consequences -- I won't elaborate beyond that," Hagari said.

He said that Israel's multi-layered aerial defense system, designed to intercept short, medium, and long-range missiles, does not provide "hermetic" protection. He urged civilians to stay alert and follow the guidelines that were tightened earlier on Tuesday, after alertness levels in Tel Aviv and Jerusalem were raised to stage 2.

White House officials said early Tuesday the missile attack could begin within 12 hours, likely after nightfall, warning that a direct Iranian attack against Israel "will carry severe consequences for Iran." The U.S. Central Command announced that three fighter squadrons are currently en route to the Middle East.

The latest developments follow weeks of escalating Israeli attacks in Lebanon, and the killing of Hezbollah leader Sayyed Hasan Nasrallah and other senior officials of the Iranian-backed group.