(NEW YORK) -- Stocks slid on Monday morning in the first trading session after the U.S.-Israeli attack on Iran over the weekend.
Four U.S. service members have been killed in action, U.S. Central Command said on Monday. At least 555 people have been killed in the U.S.-Israeli strikes on Iran, the Iranian Red Crescent Society said.
President Donald Trump announced "major combat operations" against Iran on Saturday, with daytime strikes in the joint U.S.-Israel attack targeting military and government sites, officials said.
On Sunday, Iranian state television confirmed that Ayatollah Ali Khamenei was among those killed by airstrikes in Tehran on Saturday.
The secretary of Iran's Supreme National Security Council, Ali Larijani, said that Iran is prepared for a long war.
Gen. Dan Caine, the chairman of the Joint Chiefs of Staff, did not specify a timeline, but said, "This is not a single overnight operation. The military objectives … will take some time to achieve."