Iran and the United States began a fifth round of high-stakes nuclear talks in Rome on Friday amid growing skepticism in Tehran about the chances of a deal as Washington hardens its position.

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 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.