Leaders from the United States and Iran painted a positive but cautious picture of talks between the nations over Iran’s nuclear program Saturday, after the third phase of the discussions wrapped up in Oman.

The recent U.S. deployment of B-2 bombers, the only planes able to launch the most powerful bunker-busting bombs, to within range of Iran is a potent signal to Tehran of what could happen to its nuclear programme if no deal is reached to rein it in.

Iran and the United States held their first technical-level talks on Tehran’s rapidly advancing nuclear program Saturday, a more complex phase of their high-stakes negotiations. “The negotiations this round were much more serious than in the past,