The Iranian flag waves in front of the International Atomic Energy Agency (IAEA) headquarters in Vienna, Austria May 23, 2021. (Photo: REUTERS)

US Secretary of State Antony Blinken told reporters in Stockholm that Washington had little cause for optimism and Tehran questioning the determination of US and European negotiators.

Blinken made the comments after Iran provided the European powers who are shuttling between U.S. and Iranian officials in Vienna with drafts on sanctions removal and nuclear commitments, as world powers and Tehran seek to reinstate the tattered pact.

Meanwhile his Iranian counterpart said Iran went to Vienna with serious determination, but they are not optimistic about the will and the intention of the US and the three European parties to the deal.

Talks resumed on Monday after a five-month hiatus prompted by Iran's presidential election.