WASHINGTON, March 2 (Xinhua) -- U.S. Chairman of the Joint Chiefs of Staff Dan Caine said Monday that U.S. attacks on Iran are in their early stages and more U.S. troops and fighter jets are arriving in the Middle East, suggesting an extended campaign.

"This work is just beginning and will continue," he said at a press conference at the Pentagon. "We expect to take additional losses."

For now, four U.S. servicemen were confirmed dead in the ongoing strikes, according to Caine.

He said as more fighter jets are deployed to the Middle East, the U.S. forces will be "just about where we want to be in terms of total combat capacity and total combat power."

He didn't reveal exactly how big that overall force will be.

Caine argued that the United States can "sustain the fight" against Iran. However, military officials privately have expressed concern about running low on munitions, raising the possibility that the Pentagon may have to dip into stockpiles reserved for other potential conflicts around the world, The New York Times reported.

The general said the strike killing Iran's Supreme Leader Ayatollah Ali Khamenei was carried out by Israel and supported by critical U.S. intelligence, noting the United States and Israeli forces spent months preparing for the strikes.

He also said U.S. forces conducted cyber operations to disrupt Iranian systems ahead of the initial airstrikes early Saturday. ■