By this he meant that Iran would never recognize the state of Israel or stop supporting Palestinian groups fighting what it calls “the Zionist entity.” In nuclear matters, it means accepting nothing less than full recognition of what Iran says is its “right” to a nuclear program under its own control. Support for the Syrian government will continue, as will Iran’s overall confrontational stance toward the West.

The change in Iran’s diplomatic language is a new tactic to be explored, Mr. Taraghi and others said. Iran’s supreme leader is mainly interested to see whether the United States has shifted its position and is ready to recognize Iran as a main power in the Middle East.

Suspicions of American intentions and policies lie at the core of Ayatollah Khamenei’s beliefs. “The domination system spreads war, poverty and immorality with a specific mechanism which is dividing the world between oppressors and oppressed,” he said in a speech for commanders of Iran’s Islamic Revolutionary Guards Corps last week. He said Iran’s resistance to American policies is the reason it is being pressured “by imposing sanctions, and by efforts to impose a civil war and a coup in Iran.”

Ayatollah Khamenei, who has often emphasized that he is “a revolutionary, not a diplomat,” also urged the president and his team never to forget the nature of their rivals. “It is good and necessary to have flexible approaches sometimes and somewhere,” he said, citing a theory he called “heroic leniency,” in which “you can show leniency to the rival, while never forgetting his goals.”

While many advocates of détente have interpreted this remark as illustrating Ayatollah Khamenei’s readiness to compromise, his close supporters say it means that he sees America as an eternal enemy that needs to be approached with different tactics at different times.

“Our leader is convinced the ultimate goal of the U.S. is to foil our spirit of confrontation and change our behavior,” Mr. Mousavi said. “The basis of our revolution is fighting the hegemonic powers.”

It was a surprise when Iran’s hard-liners, who had held sway for eight years in tandem with Ayatollah Khamenei, lost to Mr. Rouhani in the presidential elections in June. They and the institutions they control — the Revolutionary Guards, the nationwide Friday Prayer venues, the judiciary and the state broadcaster — have all been ordered by Ayatollah Khamenei not to sabotage Mr. Rouhani’s effort with criticism or controversial remarks.