It will take time to achieve US military objectives in Iran and additional US casualties are expected, US General Dan Caine, the chairman of the Joint Chiefs of Staff, has said, Reuters reports.

“This is not a single overnight operation. The military objectives that Centcom and the Joint Force have been tasked with will take some time to achieve, and in some cases will be difficult and gritty work,” Caine told reporters.

He added that the US continued to send additional troops to the Middle East, even after a massive military buildup.

Caine’s comments come a day after US President Donald Trump suggested that strikes against Iran could go on for the next four weeks.