Iran’s supreme leader, Ayatollah Ali Khamenei, broke his silence Monday on the protests that have engulfed the country, accusing Israel and the United States of fomenting them and expressing his support for the security services that have cracked down on the unrest.

Mr. Khamenei, speaking at a graduation ceremony at a police training school and cited by Iranian media, said it was the duty of the security forces to “ensure the safety of the Iranian nation,” referring to the protests that are now in their third week. …

“The recent incidents were orchestrated by America, the Zionist regime and the people on their payroll and Iranians who are traitors abroad,” Mr. Khamenei said. “They have a big problem with an Iran that is strong and independent.”

Mr. Khamenei’s defense of the government crackdown and his dismissal of the protests as foreign fueled suggested that the authorities are prepared to double down, a stance that may further inflame the protesters.