The US knows Iran will not agree to anything until the US lifts the sanctions, and that's why it won't lift them. And that's why it abruptly violated the JCPOA when it immediately imposed the sanctions even though Iran was in full compliance. The US wants to prevent any agreement. It's only goal is to force regime change and install a puppet government in Iran that will kowtow to US interests. The sanctions are collapsing Iran's economy and indirectly causing much death and suffering among innocent Iranian men, women, and children. That's an act of war in my book.