Russia warned against efforts to force a regime change in Iran and said it would react “very negatively” if Iran’s Supreme Leader Ayatollah Khamenei were killed, raising concerns of a broader escalation in the Israel-Iran conflict as European leaders came together with Iran on Friday for a diplomatic meeting.

Israel’s conflict with Iran is costing the country hundreds of millions of dollars a day, according to early estimates, a price tag that could constrain Israel’s ability to conduct a lengthy war. The biggest single cost are the interceptors needed to blow up incoming Iranian missiles,