Biden has already told Israel that the US will not participate in any offensive operation against Iran,

At the moment, because there is no Congressional approval for that

but Biden should also tell Netanyahu that Israel would be on its own if Iran responds to an Israeli offensive operation.

That would be GREAT, but Biden doesn't have the authority to refuse declaring war on Iran

However, as I previously said to stop the conflict Biden should offer this proposal to Israel provided Egypt agrees. Egypt will be given the West Bank enlarged by land equivalent to the Gaza Strip. In return, Israel will be given the Gaza Strip and land at least 3 times larger than the West Bank in the Sinai Peninsula. Some of the land will be adjacent to water so Israel can build desalination plants. The Sinai is inhospitable, and Egypt doesn’t have the technology to develop it, but Israel does. With its new land, Egypt can give it to the Palestinians, make it a state within Egypt, or whatever it wants.

That depends on what Congress wants

If Israel doesn't accept the proposal or it's not feasible, the UN should impose a ceasefire.

Sadly, the UN also cannot arrange a binding resolution

The only way out is for the US Congress, and other governments, to impose sanctions on Israel and threaten to fire on Israel if Israel fires on Iran. That's of course highly unlikely, given the Israel lobby's control of Congress. The only real deterrent would be the threat of a nuclear attack from Iran. I'm not sure that's possible or realistic.