There are still some "important" gaps that need to be bridged between Iran and the group of six world countries over the final text of a possible comprehensive nuclear deal, says an informed source close to the Iranian negotiating team.

�Although some parentheses (gaps) have been removed, important ones still remain,� IRNA quoted the source as saying on Thursday.

The comments came after Russian Deputy Foreign Minister and senior negotiator Sergei Ryabkov�said on Thursday that Iran and the P5+1 group of countries have worked out almost 90 percent of the text of a final deal on Tehran's nuclear program.

The Iranian source said that remarks quoted from different sources on the progress made in writing the text of a final deal could be neither�confirmed nor rejected.

�It is true that some progress has been made in removing parentheses and a considerable part of the text has been cleared from them, but the remaining parentheses in the text are all indicative of key sticking points,� the source said.

On Monday, senior Iranian negotiator Abbas Araqchi said that representatives from the two sides are working�on the�text�of a�final deal at various levels.

�The text�of�the deal is a complicated one, which has different technical, legal and, above all, political dimensions. The text must undergo full reviews, first�at the�level of experts and later at the level of deputy foreign ministers,� Araqchi said.

Araqchi, who is also Iran's deputy foreign minister for international and legal affairs, said differences over certain areas are more serious and demand more deliberation.

[caption id="" align="alignnone" width="555"] US Secretary of State John Kerry (1st R) talks with Iranian Foreign Minister Mohammad Javad Zarif in Geneva, Switzerland, on May 30, 2015. �AP[/caption]

Iranian Foreign Minister Mohammad Javad Zarif is due in the Austrian city of Vienna on Saturday to join the country�s negotiating team.

US Secretary of State John Kerry will also fly to Vienna on Friday to attend the talks, the State Department has said.

Representatives from Iran and the P5+1 group � the US, the UK, France, China and�Russia plus�Germany � are holding extensive talks to finalize the text of a possible deal over Tehran�s nuclear program by the end of June.

The two sides seek�to seal a comprehensive deal based on a mutual understanding on the key parameters agreed upon�in the Swiss city of Lausanne on April 2.

By Press TV