Global powers wrestling to hammer out a ground-breaking deal with Iran to curb its nuclear ambitions are moving complex talks into high gear with a "critical" three weeks left for an accord.
The main players -- US Secretary of State John Kerry, his Iranian counterpart Mohammad Javad Zarif and outgoing EU foreign policy chief Catherine Ashton -- will crisscross the globe ahead of the November 24 deadline seeking to narrow the gaps.
Ashton will first meet in Vienna on November 7 with political directors from the so-called P5+1 grouping -- Britain, China, France, Russia and the United States as well as Germany -- her spokesman Michael Mann said.
She will then fly to Oman to meet with Kerry and Zarif in closed meetings, in the country that first hosted secret talks between old foes Iran and the United States.
Those meetings between the two nations, which still do not have diplomatic ties, are credited with bringing Tehran back to the stop-start negotiations.
Kerry has warned the coming weeks will finally reveal whether the Islamic Republic is truly prepared to make the tough decisions needed to curb its suspect nuclear program and win a lifting of international sanctions.
"We have critical weeks ahead of us," Kerry told PBS television.
Any historic accord would aim to ease fears, after a decade of rising tensions, that Tehran might develop nuclear weapons under the guise of its civilian atomic program.
In return for reducing the scope of its activities and allowing closer UN inspections, Iran, which denies wanting the bom
Months of intense negotiations, including between Kerry and Zarif in mid-October in Vienna, have made some progress but appear deadlocked on the key issues of uranium enrichment and the pace of any sanctions relief.
Enrichment renders uranium suitable for nuclear power generation and other peaceful uses but also, at high purities, for a nuclear bomb.