Iran nuclear talks: Optimism as deadline is extended 24 November 2014 Last updated at 23:51 The US and Iran say they are confident of reaching a deal over Tehran's nuclear programme after agreeing a seven-month extension to talks. Iranian President Hassan Rouhani said a deal was close but US Secretary of State John Kerry warned that several points of disagreement remained. Six world powers want Iran to curb its nuclear programme in return for the lifting of economic sanctions. John Kerry said there are still some "significant points of disagreement" Speaking in Tehran on Monday evening, President Rouhani said the gap between the two sides had "narrowed" during the latest round of talks in Vienna. "It is true that we could not reach an agreement but we can still say that big steps have been taken," he said in an interview broadcast on state television. Mr Kerry was more cautious, warning that although "substantial progress" had been made there are still "some significant points of disagreement." These talks are not going to get easier just because we extend them. They're tough. They've been tough. And they're going to stay tough," he told reporters in Austria's capital. Analysis: Jeremy Bowen, BBC News, Vienna In a joint statement, Iranian Foreign Minister Mohammad Javad Zarif and EU envoy Catherine Ashton said that based on "the new ideas which continue to be explored" they are convinced a "comprehensive solution can be reached." "We intend to build on the current momentum in order to complete these negotiations within the shortest possible time," the statement read. Although Mr Kerry declined to comment on the details of the negotiations, President Rouhani said the talks had shown there was "no doubt for anyone that enrichment will continue in Iran." The remaining sticking points are thought to be: Speaking to the BBC, UK Foreign Secretary Philip Hammond said the failure to agree a deal was "a disappointment, but rather than continue blindly we have to recognise the reality that we're not going to make a deal tonight." However, the International Atomic Energy Agency (IAEA) says it has been unable to confirm that Iran's activities are exclusively for peaceful purposes. The UN Security Council has adopted six resolutions since 2006 requiring Iran to stop enriching uranium, with sanctions to persuade Iran to comply. Both Saudi Arabia and Israel are vehemently opposed to Iran acquiring nuclear weapons. In the US, three influential Republic senators, John McCain, Lindsey Graham and Kelly Ayott, called on President Barack Obama to "tighten the economic vice on Tehran" through new sanctions.