Iran is waiting for a message from the U.S. Specifically, for the U.S. military to lift the blockade on the Strait of Hormuz. The U.S. has actually figured out Iran's bottom line. If the U.S. military opens the strait, Iran will join the peace talks. Vance set out early because he believes the initiative is on his side. The whole world is waiting for Iran to announce its participation in the second round of peace talks, but Iran is actually waiting for the U.S. to lift the blockade first. Iran doesn’t want to treat the U.S. lifting the blockade as a bargaining chip, and the U.S. doesn’t want Iran to treat the blockade as a bargaining chip either. The U.S. really knows how to play the game. Originally, if one side made a concession, the other side should make one too. Now, the U.S. has taken a step forward first, so when they step back later, it will count as a concession. I think this is roughly why Vance didn’t get approval but still confidently set out. Because when the U.S. military opens the strait, it’s entirely up to the U.S. to decide. The U.S. has already seized the upper hand in the negotiations. Just speculation, not necessarily accurate.