Iran's talks with world powers on curbing its nuclear program in exchange for an end to sanctions could be extended for another six months if no deal is reached by a July 20 deadline, a senior Iranian official said, according to Reuters.

U.S. and Iranian officials held talks in Geneva on Monday, June 9, to tackle ways of breaking a deadlock which has raised the likelihood that the deadline will lapse without a deal meant to head off the risk of a Middle East war over the nuclear issue.

But while the diplomacy continues doubts still remain over whether Tehran and Washington can in the end overcome their longstanding differences.

The negotiations ran into difficulty last month with each side accusing the other of making unrealistic demands, raising doubts about prospects for a breakthrough next month.

An extension should be possible, Reuters says, but U.S. President Barack Obama would need to secure the consent of Congress at a time of fraught relations between his administration and lawmakers.

Iran, the United States, Britain, France, Germany, Russia and China included the July 20 deadline to reach a comprehensive agreement in an interim deal they reached in Geneva on Nov 24, under which Iran suspended some nuclear activities in exchange for limited sanctions relief - allowed for a six-month extension if more time were needed for a settlement. An extension would allow up to half a year more for limited sanctions relief and restraints on Iranian nuclear work.

Iranian Deputy Foreign Minister Abbas Araqchi spoke of a possible extension to the talks in remarks in Geneva to Iranian media on the sidelines of meetings with senior U.S. officials and the European Union's deputy chief negotiator.

"We hope to reach a final agreement (by July 20) but, if this doesn't happen, then we have no choice but to extend the Geneva deal for six more months while we continue negotiations," Araqchi was quoted as saying by Iran's state news agency IRNA."

"It's still too early to judge whether an extension will be needed. This hope still exists that we will be able to reach a final agreement by the end of the six months on July 20."

The No. 2 U.S. diplomat, Deputy Secretary of State Bill Burns, and Under Secretary of State Wendy Sherman, the primary U.S. negotiator with Iran, met an Iranian delegation led by Araqchi in Geneva on Thursday.

U.S. State Department deputy spokeswoman Marie Harf said the "wide-ranging" session ran for over five hours. "They will reconvene tomorrow morning and expect to meet all day," she told reporters in Washington, as part of consultations before the next round of Vienna negotiations scheduled for June 16-20.

Araqchi, speaking later to the Iranian student news agency ISNA, described the atmosphere of Monday's talks with the Americans as "positive and constructive".