US President Donald Trump has issued a stern warning about the dire consequences that would result if Iran attacks the United States.

Israel and Iran traded fire for a third straight day on Sunday, with rising casualties and expanding targets marking a sharp escalation in the conflict between the longtime adversaries. Overnight Iranian strikes killed at least ten people in Israel,

President Donald Trump said early on Sunday that if Iran attacks the United States in any way, it would face the might of the US military “at levels never seen before.”

The United States is the main international backer of Israel, Iran's biggest regional foe. It is also a close ally of Sunni Gulf monarchies which for years pursued their own rivalry with the Islamic Republic, seeing it as their main regional threat.

In sweeping attacks that started early Friday, Israel has struck at the regime in Tehran, targeting Iranian nuclear and military assets. The Israeli strikes have killed more than 70 people, including four top security chiefs, and damaged Iran’s main nuclear site at Natanz.

Experts suggest the U.S. has a strategic opportunity to leverage Iran's weakened position for a nuclear deal after Israel's targeted strikes on Iranian nuclear and military sites.

Iran launched dozens of ballistic missiles toward Israel on Friday night in retaliation for Israel's surprise attack early Friday. Israel struck at the heart of the Iran's nuclear program, killing several nuclear scientists as well as high-ranking military leaders, according to Israeli officials.

Israel's operation against Iran is projected to last "weeks, not days," with implicit US approval, according to White House and Israeli officials.