The eighth round of talks in the Austrian capital is resuming on Monday with the teams focusing on the verification of sanctions removal and how to evaluate US remedial measures.
Iran and P4+1 will resume talks later today in Palais Coburg after the talks were paused due to New Year's holiday for three days.
A European source who asked not to be identified told IRNA correspondent in Vienna that the last two rounds of talks have been held in a good environment and all the teams were serious and in interaction with each other.
The negotiating teams had constructive conversations on sanctions and nuclear issues and are seriously trying to reduce disagreements and so-called parentheses, the source said.
The source also said that last week's talks were focused on sanctions removal in two areas of verifications and assurances, adding that the talks were in the right direction and needed to speed up to reach a result.
Almost all negotiating teams expect the talks to conclude within the coming weeks, the source said, noting that the Islamic Republic of Iran had emphasized since the the very beginning of the talks that it must be guaranteed that no future US administration could leave the deal and impose new sanctions against Iran if the 2015 nuclear deal was to be revived.
The source said that Iran's demands had political and legal dimensions and that all participants have agreed that the demands should be included in the text of the deal in some way.
The teams are busy with the details and who should do what, how, and when, according to the source who also added that these questions are technical and complicated, but a conclusion is not so distant.
The source went on to say that all participants agreed on the verification of sanctions removal and nuclear issues.
The IAEA was responsible to verify implementation of Iran's nuclear commitments, but the verification of sanctions removal was a difficult issue, since the measures the US would take to remove sanctions should be evaluated once the US decided to do so, as said by the European source.
The source described Iran's demand for effectively removing sanctions as a natural expectation and noted that all participants agree on principles.
The European source didn't rule out the possibility that the talks may fail, but emphasized that the most likely scenario was that the talks would have a conclusion because it was hard to imagine that the delegations would be willing to leave Vienna without a deal.