France's foreign minister has said that differences in approach between some of the world powers and Russia had appeared in the last few days during negotiations over Iran's nuclear programme.
Speaking to parliament's foreign affairs committee on Tuesday, Laurent Fabius also said none of the major outstanding issues in the talks had been agreed.
Fabius also said that the United States wanted foreign ministers from six major powers known as the P5+1 to join the negotiations in the Austrian capital, Vienna.
Iran and P5+1 - the United States, Russia, France, Germany, China and Britain - have less than two weeks to bridge wide differences on the future scope of Iran's enrichment programme and other issues if they are to meet a self-imposed July 20 deadline for a deal.
They resumed talks in Vienna last week and their negotiators continued meetings in the Austrian capital on Tuesday.
Iran insists it needs to expand its capacity to refine uranium to fuel a planned network of atomic energy plants.
Amid the talks, Iran's supreme leader Ayatollah Ali Khamenei said on Tuesday that Islamic republic would need to significantly increase its uranium enrichment capacity.
Iran says its programme is for civilian purposes such as electricity generation, but the West suspects that the Islamic republic may build an atomic bomb.
Last week, Western diplomats said Iran had reduced demands for the size of its future nuclear enrichment programme in the negotiations, although Western governments were urging Tehran to compromise further.
US Secretary of State John Kerry and other foreign ministers from the six powers may travel to Vienna soon to join the talks, the Reuters news agency reported.
"The ministers can help negotiate an extension of the negotiations, if that's deemed useful, and they could help generate momentum to get a deal by July 20, which remains our goal," a Western close to the talks diplomat told Reuters on condition of anonymity.
A preliminary deal struck in Geneva between Iran and the West last November gave Tehran limited sanctions relief to buy time for negotiating a comprehensive agreement in exchange for suspending some of its most sensitive atomic work.