They don't call them the world power for nothing you know.
Without Nukes, the Iranians are holding up their defense pretty well and even fighting back, so imagine if they've got some of those in their Arsenal. The thing about these Nukes is that, you just might not know how much damage those things can inflict. And that's exactly what the US is trying to avoid, using Israel as a camouflage to do their thing and still appear to be appear to be ones proposing peace.
I see that the US isn't really interested in hurting nobody in Iran, thus their reason for proposing a peace talk, if Iran was so interested in putting an end to all the killings and attacks, then they'll just accept the treaty and then maybe come to reasonable terms with the US and all these would end in no time.
The aggressor here is Israel. There were supposed to be negotiations in a few days about Iran's nuclear programs, but Israel began to attack Iran, kicking some impotent personalities and destroying key infrastructure. If Israel stops attacking, I am sure Iran will also cease fire. But you don't expect Iran to go back to the negotiation when they are under fire.
I am surprised you think the US is not interested in hurting anybody when about 220 Iranians have been killed and more have been wounded. Israel was able to achieve it with the backing of the US.
First Israel made a very big mistake by attacking Iran after a discussion of a negotiation and is very bad, when two people are fighting and they are being told to stop fighting and embrace peace and the other hit the other it shows the one that hit the other still want to fight more, from the action of Israel it is clear that they still want to fight Iran and I really don't know what they will achieve by not stopping, the US government is the world power and as a world power one of the things you should do is to make peace and make sure things don't go out of hand, the US government should find
a way and end
to this war immediately because is not funny anymore, a lot of people has dead and properties has been destroyed.
I really don't know if the US government was the one that carried out the attack on Iran that lead to the killing of 220 Iranians, however since the US government is of the biggest support of Israel is possible they helped out in the attack but no one is still very sure of it, but if truly the US government is involved then I'm highly disappointed at them.