By Arshad Mohammed
ISTANBUL (Reuters) - Secretary of State John Kerry said on Sunday world powers would pursue further talks with Iran to resolve a decade-old dispute over its nuclear program, but stressed that the process could not go on forever.
The six powers and Iran failed again to bridge wide differences at weekend talks in Kazakhstan, prolonging a stand-off that could yet erupt into a new Middle East war. No new talks were scheduled.
"This is not an interminable process," Kerry said after arriving in Istanbul on Sunday on the first leg of a 10-day trip to the Middle East, Europe and Asia.
He said U.S. President Barack Obama was committed to continuing the diplomatic process despite what he called the complicating factor of an Iranian presidential election in June.
"Diplomacy is a painful task ... and a task for the patient," Kerry told a news conference.
Western powers suspect Iran is trying to develop the means to produce nuclear weapons under the guise of a declared civilian atomic energy program. Iran denies the accusation.
Israel urged the powers to set a deadline of weeks for military action to persuade Iran to halt its uranium enrichment activity. Prime Minister Benjamin Netanyahu, evoking Iran during a speech at a ceremony for Israel's Holocaust remembrance day, hinted that Israel would act alone if necessary.
"What has changed since the Holocaust is our determination and our ability to defend ourselves," he said. "We appreciate the international community's efforts to stop Iran's nuclear program, but at no stage will we put our fate in the hands of others, even our closest friends."
Tehran accuses Israel of threatening peace in the region and refuses to recognize the Jewish state, which is widely believed to harbor the Middle East's only nuclear arsenal.
European Union foreign policy chief Catherine Ashton, who represents the United States, Russia, China, France, Britain and Germany in talks with Iran, said the two sides had failed to resolve key differences during the two-day talks in Almaty.
"... It is important to continue to talk and to try to find common ground," Kerry said. "So we hope that out of Almaty will come a narrowing of some of the differences. We remain open and hopeful that a diplomatic solution can be found."
DEMAND FOR ENRICHMENT SUSPENSION
The six powers want the Islamic Republic to suspend its higher-grade uranium enrichment work in return for modest relief from international sanctions, an offer Iran did not accept.
Iran's most powerful figure, Supreme Leader Ayatollah Ali Khamenei, who has the last say on all state matters, has shown no sign of willingness to scale back Iran's nuclear activity.
"As a member of the Non-Proliferation Treaty (NPT), Iran has the right to enrich uranium ... The Islamic Republic will never stop its enrichment work," the head of parliament's Foreign Affairs and National Security Committee, Alaeddin Boroujerdi, said, according to Iran's ISNA news agency.
Boroujerdi was not speaking on behalf of Khamenei, whose stamp of approval is required for any substantive Iranian decision in the nuclear dispute.
But he also suggested that the Islamic Republic might even enrich uranium above the 20 percent level of fissile purity "for specific projects", a move that would increase alarm in Western capitals. He did not elaborate.
Iran says it is refining uranium to 20 percent - well above the 5 percent suitable for nuclear power stations - to convert into special fuel for Tehran's medical research reactor.
But 20 percent is a significant technical advance toward the bomb-grade threshold and some analysts believe Iran now has enough of this material to run the reactor for many years, raising Western suspicions that the growing stockpile may really be a potential reserve for weapons.
Some diplomats and experts have said Iran's June presidential election has raised uncertainty in the West over the Islamic Republic's strategy for nuclear diplomacy.
"Obviously there is an election and that complicates the choices with respect to the politics of Iran, and we are aware of that," Kerry said.
"But we will continue. The president (Obama) has determined to continue to pursue the diplomatic channel ... We remain open and hopeful that a diplomatic solution can be found."
(Reporting by Arshad Mohammad; Writing by Parisa Hafezi; Editing by Mark Heinrich and Kevin Liffey)