Iran’s initial response to the U.S. proposal to end the war, which was conveyed to Pakistan, was that it was "one-sided and unfair," a senior Iranian official told Reuters on Thursday, adding that a path forward might still be found if realism prevailed in Washington.

The official said the proposal "was reviewed in detail on Wednesday night by senior Iranian officials and the representative of Iran’s Supreme Leader."

"In brief, the proposal suggests that Iran would relinquish its ability to defend itself in exchange for a vague plan to lift sanctions," he said, adding that the proposal lacked the minimum requirements for success.

He said there was "still no arrangement for negotiations, and no plan for talks appears realistic at this stage," while Turkey and Pakistan were trying to help "establish common ground between Iran and the United States and reduce differences."