"Lying and cheating in the Arab world is not really a moral matter but a method of safeguarding honor and status, avoiding shame, and at all times exploiting possibilities, for those with the wits for it, deftly and expeditiously to convert shame into honor on their own account and vice versa for their opponents. If honor so demands, lies and cheating may become absolute imperatives.” [David Pryce-Jones, “The Closed Circle” An interpretation of the Arabs, p4]
“No dishonor attaches to such primary transactions as selling short weight, deceiving anyone about quality, quantity or kind of goods, cheating at gambling, and bearing false witness. The doer of these things is merely quicker off the mark than the next fellow; owing him nothing, he is not to be blamed for taking what he can.” [David Pryce-Jones, “The Closed Circle”, p38]
In Shia Islam, there is a concept known as taqiyya.
It permits lying.
It encourages lying if it is good for Shiites.
Iran is a Shia superpower.
Just know that it does not bother them, shame them, or embarrass them to lie. To anyone at anytime. It is, rather, expected that they will lie.
So tap the brakes on these discussions about their nukes and their willingness to open up for inspection.
They will literally lie till death. It's what their religion teaches.