Iran on Friday ruled out resuming nuclear negotiations with the United States until Israel ends its airstrikes, as the head of the Israeli military warned the escalating conflict could stretch on for weeks and U.S. President Donald Trump weighed possible American involvement.

A series of blasts shook Tehran on Friday as Iran activated air defenses and launched missiles at Israel, which continued its bombardment of Iranian targets. The escalation came as Israeli military chief Lt. Gen. Eyal Zamir warned the conflict could become a drawn-out campaign.

“We must be ready for a prolonged campaign,” Zamir said in a video statement, eight days after Israel began a wave of strikes it said were aimed at halting Iran’s nuclear ambitions — an accusation Tehran denies.

“The campaign is not over. Although we have made significant achievements, difficult days still lie ahead,” he added.

As President Donald Trump weighs U.S. involvement in the conflict, top European diplomats met with Iranian Foreign Minister Abbas Araghchi in Geneva, seeking to defuse tensions and revive nuclear talks.