I don't think that this offer is an offer to Iran, but it is an offer to silence the voices wanting direct US-Iran talks. Some others characterize it as a "poison pill" and a nonstarter.
Do you know what I would have done if I was a policy maker in Iran? I would have accepted the offer, saying that "Iran will suspent its nuclear program for 30 days as a good faith effort from the day the negotiations start. If the United States (that has never dropped its allegations) provides us with a verifiable proof that our nuclear program is aimed at weaponization, we will make the suspension permanent."
This way the ball (that is now in Iran's court) rolls back to the United States' court. And also Iran will manoeuver over the fact that the accusations are not founded on verifiable facts.
The starter for this post was a post by Mehdi (in Persian).