Talks among the top diplomats of six world powers and Tehran are under way in Switzerland concerning Iran's controversial nuclear program.
U.S. Secretary of State John Kerry arrived in Geneva Saturday after an overnight flight from Washington to join the discussions that may be on the verge of a breakthrough to defuse the decade-old standoff. He immediately went into a series of talks with other top diplomats.
Foreign diplomats from the group known as the P5+1 - the United States, Britain, China, France, Russia and Germany - are gathering in Geneva for the intense discussions.
British Foreign Secretary William Hague said Saturday that "difficult negotiations" remain, as there are narrow, but "important gaps." German and French diplomats also said there is still tough work ahead before a deal can be reached.
Chinese officials said Saturday talks have reached a "final phase."
European Union foreign policy chief Catherine Ashton has been leading the negotiations with the Iranians. The main sticking points have been to what extent Iran will be allowed to enrich uranium and how much sanctions would be eased.
Iran insists it keeps the right to enrich uranium and denies it wants to build a nuclear weapon. It has offered to suspend parts of its nuclear program and agreed to tighter inspections if the West relaxes sanctions that have devastated its economy.
Under discussion is a first-phase agreement meant to build trust while the two sides work out a more comprehensive deal that would ease Western concerns about Iran's ability to build nuclear weapons.
Iran's news agency IRNA on Friday called the talks "complicated and tough."
So far, the U.S. has said it is prepared to offer what it calls limited and reversible sanctions relief, including unfreezing billions of dollars in Iranian funds overseas. Iran has said it would also like restrictions eased on its oil exports and banking sector.
Former White House official and arms control specialist Gary Samore told VOA's Persian News Network Friday that resolving the nuclear issue is just one part of improving the relationship between the U.S. and Iran. He said the two nations continue to have disagreements on other issues, including Syria and the Israeli-Palestinian conflict.
U.S. lawmakers are threatening to increase sanctions if a deal is not reached. U.S. Senate Majority Leader Harry Reid said Thursday he is committed to moving forward in December with a bill to impose new measures on Iran if negotiations are not successful.
President Barack Obama and Secretary of State Kerry have been asking key congressional leaders to hold off on any new sanctions against Tehran while the Geneva talks continue.
This is the third round of negotiations between Iran and the P5+1 group.
The latest talks began Wednesday, building on a prior round of negotiations that ended two weeks ago. Analysts say those talks failed in large part because of objections by France.