The foreign ministry said the ongoing negotiations with the major powers over Iran's nuclear program have reached a "complicated stage."
"The talks have reached a very complicated and critical stage," the foreign ministry spokesperson said on Wednesday.
"We are witnessing the negotiating team's continual effort, who have days of intensive work ahead of them,… to narrow the gaps," IRNA quoted Marzieh Afkham as saying at her regular press briefing.
Her remarks came amid a new round of talks between the Iranian, US and EU delegations, which started in the Swiss city of Lausanne on Sunday, in search of an agreement which would place constraints on Tehran's nuclear activities for a specified period of time in exchange for the lifting of sanctions.
The political directors of Iran and the P5+1 (the five permanent members of the UN Security Council plus Germany) also held a meeting in the Swiss city on Wednesday.
Afkham confirmed the remarks by Atomic Energy Organization of Iran Director Ali Akbar Salehi that there has been great progress in discussions on technical aspects, adding that the talks relating to "political issues and sanctions" are still being pursued.
Salehi said on Tuesday there is agreement on "90 percent of technical issues."
In Lausanne, Foreign Minister Mohammad Javad Zarif told reporters that the negotiating parties should back up their words with action so that a long-term accord can be achieved.
In an answer to a question as to whether there is any political will on the part of the other side to reach an agreement, the chief nuclear negotiator said, "Everybody claims there is political will… However, (this) should be seen in action."
On the progress made so far, the senior negotiator said, "On some issues we have approached a common understanding while on others there is a longer way to go."
