Ayatollah Khamenei, the supreme leader of Iran, said today there is no guarantee there will be a final deal after negotiations on its nuclear programme with world powers.
Mr Khamenei said in a statement "it is possible that the untrustworthy side [the P5+1] wants to restrict our country in the details".
"I have never been optimistic about negotiating with America. While I was not optimistic, I agreed with this particular negotiation and supported the negotiators," the statement went on.
The supreme leader and President Hassan Rouhani said Iran would not sign a final deal unless sanctions were lifted "on the first day" of implementation.
The proposed agreement says Iran will cut its stockpile of enriched uranium and the number of centrifuges it runs, in return for a phased lifting of UN, US and EU sanctions once the International Atomic Energy Agency (IAEA), confirms Iranian compliance.
American officials clarified on Monday that sanctions would have to be lifted in phases.
"It has never been our position that all of the sanctions against Iran should be removed from day one," said White House spokesperson Josh Earnest.
Parameters of the agreement, published by the State Department state U.S. sanctions on Iran for terrorism, human rights abuses, and ballistic missiles will remain in place under the deal.
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