As joint U.S.-Israeli strikes against Iran continue under Operation Epic Fury, President Donald Trump told the Daily Mail on Sunday that the campaign could extend for as long as a month.

The president spoke from Mar-a-Lago following a televised address in which he mourned three U.S. service members killed in the operation and expressed condolences to their families.

“It’s always been a four-week process,” Trump said. “We figured it will be four weeks or so. It’s always been about a four-week process — as strong as it is, it’s a big country. It’ll take four weeks — or less.”

Trump said he has not been surprised by the results of the strikes so far.

“No, I think it’s going as planned,” he said. “Other than we took out their entire leadership — far, far more than what we thought. Looks like 48.”

The president reiterated that he remains open to negotiations with Iran, though he could not say when talks might begin.

“I don’t know,” Trump said. “They want to, they want to talk, but I said you should have talked last week, not this week.”

Trump is scheduled to return to the White House later Sunday ahead of what aides expect will be another intense week of developments.

Asked whether he believes Iran could one day become a peaceful, democratic nation, Trump expressed cautious optimism.

“I do,” he said. “It’ll be very interesting to watch, but a lot of things could happen — and a lot of very positive things could happen.”