LAUSANNE, Switzerland -- Iran and six world powers broke off nuclear negotiations ahead of schedule Friday to allow members of the Iranian delegation to attend the funeral of their president's mother, as a senior Russian official suggested that the sides were close to a deal.

Top Russian negotiator Sergey Ryabkov told The Associated Press that while some disputes remain, negotiators were expected to "finish their main work" before the talks resume next week. He spoke shortly before U.S. Secretary of State John Kerry wrapped up five days of meetings of with Iranian Foreign Minister Mohammad Javad Zarif.

The negotiations had been tentatively extended to go into Saturday. But the Iranian delegation decided to depart for home later Friday to allow negotiators, including Zarif and Hossein Fereydoon, a brother of Iranian President Hassan Rouhani, to attend the funeral of Rouhani's mother.

Kerry issued a statement extending condolences to Rouhani and his family with the death coming at the time of the Persian New Year. "Such a loss is especially hard coming on the eve of Nowruz, traditionally a time when families gather together in joy and hope. We share in his grief and that of his brother," Kerry said.

Meanwhile, President Barack Obama issued a statement calling for the return of Americans held in Iran with the Nowruz holiday. "It is a time for reuniting and rejoicing with loved ones and sharing hopes for the new year," he said.

Obama said that Iran should immediately release U.S. prisoners Saeed Abedini of Boise, Idaho; Amir Hekmati of Flint, Michigan; and Jason Rezaian of Marin County, California. Obama also said Iran should help find Robert Levinson, a former FBI agent who went missing eight years ago from the Iranian resort of Kish Island.

The White House has said U.S. negotiators have brought up the return of the Americans held in Iran on the sidelines of the talks, but they don't plan to make their return a part of the negotiations over Tehran's nuclear program.

Ryabkov's comments on the progress being made jibe with those of other officials who told the AP earlier that the United States and Iran are drafting elements of a deal that commits Tehran to a 40 per cent cut in the number of machines it could use to make an atomic bomb. In return, the Iranians would get quick relief from some crippling economic sanctions and a partial lift of a U.N. embargo on conventional arms.

Agreement on those details of Iran's uranium enrichment program could signal a breakthrough for a larger deal aimed at containing the Islamic Republic's nuclear activities.

The sides ultimately want to reach a full agreement by the end of June. In Brussels, French President Francois Hollande, British Prime Minister David Cameron and German Chancellor Angela Merkel discussed the state of negotiations Friday with the EU's top diplomat, Federica Mogherini.

Ryabkov said earlier that foreign ministers of those three nations were considering joining the talks in Lausanne, but the decision by the Iranians to leave Friday took that option off the table.

Instead, Western consultations were moving elsewhere. U.S State Department spokeswoman Marie Harf said Kerry -- who has done most of the negotiating directly with Zarif -- would meet the French, British and German foreign ministers somewhere in Europe Saturday ahead of a new full round next week. The ISNA news agency in Iran said talks would resume Wednesday. Diplomats said the venue would likely be somewhere in Switzerland.

Iran is negotiating in Switzerland with the United States, Russia, China, Britain, France and Germany, with an end-of-March deadline to reach a preliminary deal for Iran to scale back its nuclear program in return for an easing of economic sanctions. Iran insists it is not trying to build a nuclear bomb, but the West is skeptical.

The negotiations build on a deal struck in late 2013 that committed Tehran to temporary restrictions while the present negotiations continue. A confidential International Atomic Energy Agency report issued Friday and shared with the AP said Iran was honouring those commitments.