VIENNA, July 16. /ITAR-TASS/. The currently ongoing round of talks between Iran and the six international negotiators on Tehran’s nuclear program may end July 18, but the parties seriously discuss extending the negotiating process, a diplomatic source in the Iranian delegation said Wednesday.

“The current round may end already on Friday [July 18],” the source said. “The sides are seriously discussing the possibility to extend the negotiating process after July 20, which means changing the deadline when a comprehensive agreement should be drafted.”

“The terms of extending it are not clear yet,” the source added. “It may be weeks or months. This is currently discussed.”

Earlier, another representative of the Iranian delegation told ITAR-TASS that the negotiating process might be extended up to November 25, when it would be a year since the adoption of the Geneva agreement. Upon mutual consent of the parties, the negotiations may be prolonged until this date.

Two weeks after the start of the current round, which was supposed to be the final one, Iran and the six world powers have not yet come to agreement on key aspects of Tehran’s nuclear program.

What seemed highly unlikely at the beginning of the month can be more and more often heard from diplomats and chief negotiators: the sides may fail to agree the final document by July 20.

Even the heads of the delegations and ministers participating in the talks have stopped making forecasts. After three days of intensive consultations in Vienna, US Secretary of State John Kerry said before flying home on Tuesday, July 15, that the chance to reach an agreement remained but all the same he would discuss a possible extension of the talks with US President Barack Obama and Congress.

Iranian Foreign Minister Mohammad Javad Zarif was even less optimistic and said getting the agreement by July 20 was just a possibility and noted that Tehran had not decided yet whether it should continue the talks after July 20.

As diplomatic sources said before the start of the talks, much in their final rounds would be decided in consultations between Iran and the United States. But the tone of Kerry’s and Zarifi’s statements indicates a lack of progress up to date.

A source in the Iranian delegation sad Tehran’s enrichment program was the main stumbling block at the talks. It was made clear to the Iranian delegation in Vienna that 19,000 centrifuges would be too much for an enrichment program.

However, Zarif said on Tuesday, July 15, that Tehran would not give up its goal of having a serious but transparent enrichment program to meet the needs of the country. He stressed that the Iranian nuclear program was peaceful and Tehran had nothing to hide.

Another source in the delegation told ITAR-TASS that the lifting of a part of sanctions as an interim step would not satisfy Iran. He stressed that if the six world powers wanted to achieve substantial progress at the talks, the sanctions must be lifted in full.

It’s too early to say whether Iran and the P5+1 (five permanent members of the U.N. Security Council and Germany) group can come to agreement by July 20, an Iranian diplomat said.

A source close to the talks said that the negotiations between Iran and the United States were proceeding intensively but there were no significant changes in their positions yet.