Differences have emerged among the members of the Group 5+1 (the US, Russia, China, Britain and France plus Germany) after Washington troubled drafting a final comprehensive agreement with Iran during the recent nuclear talks in Vienna, sources said on Sunday. Informed sources privy to the talks told FNA on Sunday that some members of the G5+1 have protested at the US for ignoring the agreements struck with Iran in the Vienna 3 meetings in New York (in April and early May) which called for starting drafting a final deal from this stage. Sources said the talks ended without a result after Washington raised excessive demands from Iran contrary to the agreements which were made in the previous rounds of meetings. They warned that if the situation continues, the G5+1 will eventually lose its function and collapse. Iran and the Sextet of powers wrapped up their fourth round of talks in Vienna on Friday. The Iranian negotiators had several rounds of bilateral talks with the delegations of the EU and the Group 5+1, including a rather lengthy meeting with the US team, during their three-day-long talks in the Austrian capital. On the third day of the Vienna talks, a senior diplomat close to the Iranian team of negotiators urged the Western states to stop their excessive demands, reiterating that Iran is standing firm on its rights. "The West should give up its excessive demands and gather a precise assessment of the realities existing on the ground," the diplomat told FNA in Vienna on Friday afternoon, stressing that the policy of pressuring Iran has always proved futile and backfired. The source said the Iranian negotiators have come to Vienna to establish the nation's rights, reiterating that they would never retreat along this path. He said "difference in views, specially around such a vital discussion as Iran's nuclear issue, is considered to be natural", but "given the recent developments, the western states are displaying that they are not practicing the pragmatism that seemed to have developed in them to a certain level". Yet, the diplomat underlined that "the window of opportunity is still open for the western parties to step onto the realm of pragmatism". Last week before heading to Vienna for talks with the G5+1, Iranian Foreign Minister Mohammad Javad Zarif once again underlined that a final deal with the world powers must guarantee the Iranian nation's inalienable nuclear rights. "Any final nuclear agreement with the G5+1 must create an opportunity for Iran to exercise its inalienable right to use peaceful nuclear energy," Zarif said in a meeting with former Director General of the International Atomic Energy Agency (IAEA) Hans Blix in Tehran.