General Jafari advised Mohammed Javad Zarif to keep out of military issues, declaring: “We consider him an experienced diplomat, but he has no experience in the military field.”
Mr Zarif, an urbane, US-educated diplomat, was Iran’s chief negotiator in the landmark deal struck with world powers last month under which Tehran is to curb its nuclear programme in exchange for some respite from crippling sanctions.
His domestic critics say he offered too much for too little in return.
United States president Barack Obama faces similar criticism from a largely hostile Congress.
Iranian hardliners have made Mr Zarif a lightning rod for their criticism of the moderate government of Hassan Rouhani, who took office as president in August pledging to improve relations with the West and neighbouring countries.
Gen Jafari claimed that Mr Rouhani’s administration was under the influence of Western ideas and “fundamental change” was needed.
But Iranian hardliners can only push so far. Iran’s supreme leader, Ayatollah Ali Khamenei, while deeply suspicious of the US, has endorsed Mr Rouhani reaching out to the West.
Mr Zarif was quoted by local media last week as saying that the West feared the might of the Iranian people, rather than its military defences, which he said the US could destroy with a single bomb if it wished.
Mr Zarif later said this and other contentious comments attributed to him had been skewed or taken out of context and he accused his hardline critics of “slander, profanity and insults”.
Gen Jafari’s intervention flouted polite but pointed calls by Mr Khamenei in September for the Revolutionary Guards to stay out of politics.
“The main threat to the revolution is in the political arena and the Guards cannot stay silent in the face of that,” Gen Jafari said.
He added Iran would not relent in its support of its key Arab ally, president Bashar al-Assad of Syria.
Meanwhile, Gen Jafari said Iran’s missiles can reach Israel. But he maintained that Iran’s restraint meant the US and Western Europe were beyond Iranian strikes. “We can still upgrade the range of missiles but for the time being on the order of the supreme leader we have limited the range of our missiles to 2,000km.”
Hossein Shariatmadari, the editor of Kayhan, an influential hardline daily newspaper, accused Mr Zarif of sending a “signal of surrender” to the West.