Iran’s top diplomat warned Thursday that his country would take “special measures" to defend its nuclear facilities if Israel continues to threaten them, raising the stakes further ahead of a new round of talks with the United States.

The United States would bear legal responsibility in the event of an Israeli attack on Iranian nuclear facilities, Foreign Minister Abbas Araqchi said on Thursday, following a CNN report that Israel might be preparing strikes on Iran.

Iran’s nuclear facilities are deep underground and heavily fortified. An effective attack by Israel would require U.S. assistance for both mid-air refueling and munitions, according to the February intelligence report.