By Louis Charbonneau and Yeganeh Torbati
NEW YORK (Reuters) - New Iranian President Hassan Rouhani said on Friday he wanted talks with major powers on Iran's nuclear program to yield results in a short time, while France challenged Tehran to address Western concerns even sooner than it has proposed.
Rouhani made his remarks shortly before he left for Tehran at the end of his debut visit to the United Nations for its annual meeting of the General Assembly.
Western diplomats said he was on a charm offensive, repeatedly stressing Iran's desire for normal relations with Western powers and denying that it wanted a nuclear arsenal, while urging an end to sanctions that are crippling its economy.
Rouhani, who took office last month, told a news conference he hoped talks with the United States and five other major powers "will yield, in a short period of time, tangible results," on a nuclear deal. But he was less specific than he had been on Tuesday about the time scale.
He said Iran would bring a plan to resolve the decade-long dispute over Tehran's nuclear program, which Western powers and their allies suspect is aimed at developing an atomic weapons capability, to an October meeting with the six powers in Geneva.
He offered no details about that plan.
Referring to discrepancies in the time scales given by Rouhani and Iran's foreign minister, French Foreign Minister Laurent Fabius said there were concerns that the longer it took, the more progress Tehran could make with production of nuclear materials, despite negotiations with major powers.
Iranian Foreign Minister Mohammad Javad Zarif met with his counterparts from Britain, China, France, Germany, Russia and the United States on the sidelines of the U.N. General Assembly to discuss the nuclear issue on Thursday.
A senior U.S. official said after the meeting that Zarif had proposed fully implementing an agreement on its nuclear program within a year. Rouhani said on Tuesday he would like to see a deal with world powers in three to six months.
"The Iranian foreign minister discussed the heart of the matter. He spoke about taking a year to move forward, but I reminded him that his president had spoken about three to six months, and he said that he'd be pleased if things could be done more quickly, Fabius said after meeting with Zarif.
"I told him that we had to move quickly and that's one of the issues that needs to be dealt with, because does nuclear production continue during the negotiations?
"We can't find ourselves in a position where the discussions last a year and during this time the number of centrifuges increase, and ... the Arak reactor progressing which would be a problem," Fabius added, referring to a heavy-water nuclear reactor that could yield plutonium for atomic weapons.
TALKS WITH U.N. NUCLEAR WATCHDOG STALLED
Without making any real concessions so far, Rouhani has offered a softer, more reasonable tone than his stridently anti-Western and anti-Israeli predecessor, Mahmoud Ahmadinejad.
He has called for an end to the international sanctions imposed on Iran for refusing to halt uranium enrichment, which have begun to bite deeply.
Iranian oil exports have fallen by about 60 percent in the past two years as the European Union stopped purchases and most Asian buyers drastically cut imports because of the sanctions. Iran is now earning only around $100 million from oil sales a day as opposed to $250 million two years ago.
In Vienna, Iran held "constructive" talks with the U.N. nuclear watchdog, which has said repeatedly over the past 10 years that it cannot verify the peaceful nature of Tehran's atomic program, according to a senior U.N. official.
The International Atomic Energy Agency has long struggled to strike a deal with Tehran to enable it to resume a stalled inquiry into suspected nuclear weapons research in Iran. This is crucial for a separate process involving major Western powers, since Kerry has said the United States will not lift sanctions until it has been verified that Iran is not pursuing nuclear arms.
Rouhani said an improved mood in U.S.-Iranian relations could lead to better ties between the two countries, which have been estranged since the 1979 Iranian revolution toppled the U.S.-backed Shah.
"The atmosphere is quite different from the past," Rouhani said, speaking a day after the highest-level talks between the United States and Iran since before the revolution.
Zarif and U.S. Secretary of State John Kerry met along with other major powers on Thursday to address Western concerns over Iran's nuclear program. That was followed by a brief meeting between Zarif and Kerry.
"Our goal is the shared interest between the two nations," Rouhani said. "Our goal is resolving problems, our goal is step-by-step creating trust between the governments and peoples."
Both sides said although the tone was positive, they remained cautious about resolving the nuclear standoff.
Rouhani said Tehran would present its plan for a resolution of the issue at talks with the five permanent members of the U.N. Security Council and Germany - known as the "P5+1" - scheduled to be held in Geneva from October 15-16.
The five permanent Security Council members are Britain, China, France, the United States and Russia.
"We say explicitly that we will be transparent; we say explicitly that we will not build a bomb," Rouhani said. "Through the P5+1 we want to provide even more assurances."
Rouhani also said his government had a full mandate to handle the issue in Iran.
"I think that any result this government reaches, it will have the support of other powers in Iran," he said. "On the nuclear issue, the government has total discretion."
U.S. President Barack Obama has cautiously embraced Rouhani's gestures as the basis for a possible nuclear deal and challenged him to demonstrate his sincerity.
However, the failure to orchestrate a handshake between the two leaders, apparently because of Rouhani's concerns about a backlash from hardliners at home - and perhaps Obama's concerns about the possibility of a failed overture - underscored how hard it will be to make diplomatic progress.
(Additional reporting by John Irish in New York and Fredrik Dahl in Vienna; Writing by David Brunnstrom and Louis Charbonneau.; Editing by Christopher Wilson)