President Donald Trump declared Saturday evening that a diplomatic solution in Iran may be "much easier" after U.S.-Israeli airstrikes killed Supreme Leader Ayatollah Ali Khamenei and others in Tehran's theocratic leadership.

Trump also told CBS News in a phone interview he has been surprised by Iran's response to the attacks so far.

"We thought it'd be double," he said, though he added that the situation remains fluid. "Thus far, it's been less than we thought."

The American president declared himself pleased with the results of the first day of military action, saying it was "a great day for this country, a great day for the world."

He expressed confidence that the heavy early toll that Iran suffered may open the door for a quicker diplomatic solution.

"Much easier now than it was a day ago, obviously," Trump answered when queried about the possibility of a diplomatic solution "Because they are getting beat up badly."

Trump announced that Khamenei, Iran's ayatollah for nearly four decades, was killed in the strikes. Iran likewise announced the death.

Trump told CBS News "there are some good candidates" to lead Iran if its people want regime change.