"The other side is cunning and untrustworthy," Kamalvandi said at a press conference in Tehran on Monday.
He urged supports for "strengthening Iran's negotiating position" during the remaining time until a deadline for a lasting nuclear agreement between Tehran and the Group 5+1 (Russia, China, the US, Britain, France and Germany).
His comments came after Iran and the six powers on April 2 reached a framework nuclear agreement following more than a week of intensive negotiations in Lausanne, Switzerland, with both sides committed to push for a final deal until the end of June.
Kamalvandi also pointed to a fact sheet that Washington issued after the Lausanne talks, and said the fact sheet includes subjects that have not been yet finalized.
He stressed that the Americans have composed their fact sheet in such a way that is palatable to their own public opinion.
Following the Lausanne talks, the US Department of State issued a fact sheet that emphasized Iranian concessions and claimed that the anti-Iran sanctions will be "suspended", rather than terminated, and only after confirmation that Tehran has complied with the terms of the agreement.
However, Iranian diplomats have dismissed such an interpretation of the agreement.
According to the text of the Lausanne statement, "the EU will terminate the implementation of all nuclear-related economic and financial sanctions and the US will cease the application of all nuclear-related secondary economic and financial sanctions, simultaneously with the IAEA-verified implementation by Iran of its key nuclear commitments."