Iran and the United States made “some but not conclusive progress” in a fifth round of negotiations in Rome over Tehran’s rapidly advancing nuclear programme, the talks’ Omani mediator said.

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.

Iran and the United States are preparing for a fifth round of negotiations over Tehran’s rapidly advancing nuclear program, with enrichment emerging as the key issue

Iran’s top diplomat insisted Wednesday that Tehran will never stop enriching uranium, reinforcing the Islamic Republic’s hard line ahead of a new round of indirect talks with the United States over its fast-advancing nuclear program.