On the eve of President Hassan Rouhani’s address to the UN General Assembly, Iran’s Supreme Leader has seized center stage with a denunciation of the “Great Satan” US as “corrupt” and “lying”.

In an address at the Police Academy on Sunday, Ayatollah Khamenei soon moved from praise of graduates to the “malicious and vicious interferences led by the US and Zionists, with the intentions of penetrating the region to safeguard their illegitimate interests by weakening nations”:

One day they create Daesh [the Islamic State], the next day they resort to using some other malicious method. The latter happens when they see Daesh draw its last breaths, as a result of victory due to the resistance and willpower of pious youth.

See also An Indecisive Conflict: The State of US-Iran Relations

Calling for “a sense of power within nations and regional governments” — “If we compromise with the enemy, he will advance” — Khamenei invoked distrust of the US over the July 2015 nuclear deal:

Every day, they commit different mischievous acts. This proves the correctness of our magnanimous Imam’s statement when he described the US as “the Great Satan”. The regime of the United States of America is the most vicious devil, indeed.

The Supreme Leader’s address appears not only to challenge the US, but to ensure a firm line by President Rouhani on his trip to New York.

In the face of tougher Trump Administration rhetoric and additional US sanctions on Tehran, Rouhani has shifted to the possibilitym of an Iranian departure from the nuclear deal if the Americans withdraw. However, his emphasis has continued to be a “proportionate response” to any US actions.

In an interview with CNN, broadcast on Monday, Rouhani envisaged that the US will not leave the Joint Comprehensive Plan of Actions, while warning of the effect if they did:

Exiting such an agreement would carry a high cost for the United States of America, and I do not believe Americans would be willing to pay such a high cost for something that will be useless for them….

[Withdrawal] will yield no results for the United States but at the same time it will generally decrease and cut away and chip away at international trust placed in the Unites States of America.

However, he said the situation was uncertain “given that Mr. Trump’s actions and reactions and policies are somewhat unpredictable”. So “we have thought long and hard about our reactions,” Rouhani summarized, with the Iranian response likely to come “quite swiftly” and “probably within a week”.