The Pentagon is bracing for more casualties as it wages a massive campaign to eliminate Tehran's arsenal but acknowledged that U.S. forces cannot intercept all incoming fire.
Fifty-two percent of Americans oppose the strikes, and two-thirds say the Trump administration hasn't clearly explained the goals of the military action.
Three U.S. fighter jets involved in the offensive against Iran were shot down mistakenly by Kuwait's air defenses, the U.S. military's Central Command said.
The war in the Mideast has effectively halted shipping through the Strait of Hormuz, threatening to push up gas prices and raise the cost of other goods.
U.S. officials said they were negotiating with Iran in good faith, even if hours later they joined Israeli military strikes that targeted the Iranian government.
Three U.S. service members have been killed, and President Donald Trump said "there will likely be more" with U.S.-Israeli operations set to continue for weeks.
Trump has taken an approach to selling U.S. citizens on military action in Iran that contrasts with his predecessors, seeking to avoid completely owning it.
U.S. forces say they have hit 1,000 targets over the past two days in a race to take out Iran's ability to threaten American personnel and allies across the Middle East.
Iran intensified its strikes against countries in the Persian Gulf and Israel on Sunday, attacking at least nine countries since the start of the joint U.S.-Israeli attack.