VIENNA — Six world powers and Iran made a “good start” in talks in Vienna towards reaching a final settlement in the decade-old stand-off over Tehran’s nuclear program, although they conceded that their plan to get a deal in the coming months was very ambitious.

By late July, Western governments hope to hammer out an accord that would lay to rest their suspicions that Iran is seeking the capability to make a nuclear bomb, an aim it denies, while Tehran wants a lifting of economic sanctions.

Wide differences remain on how this could be achieved, although the two sides said on Thursday, Feb. 20, they agreed during meetings this week in the Austrian capital on what to discuss and a preliminary timetable for the talks on such an accord.

“We have had three very productive days during which we have identified all of the issues we need to address in reaching a comprehensive and final agreement,” European Union foreign policy chief Catherine Ashton told reporters.

“There is a lot to do. It won’t be easy but we have made a good start,” said Ashton, speaking on behalf of the United States, Russia, China, France, Britain and Germany.

Senior diplomats from the six nations, as well as Ashton and Iran’s Foreign Minister Mohammad Javad Zarif, will meet again on March 17 in Vienna to have a series of further discussions ahead of the July deadline.

Tehran denies that its nuclear program has any latent military purposes and has signaled repeatedly it would resist dismantling its nuclear installations as part of any deal.

“I can assure you that no one had, and will have, the opportunity to impose anything on Iran during the talks,” Zarif told reporters.

A senior U.S. official who asked not to identified cautioned that the exchanges with Iran would be “difficult” but the sides were committed to reaching a deal soon.

“This will be a complicated, difficult and lengthy process. We will take the time required to do it right,” the official said. “We will continue to work in a deliberate and concentrated manner to see if we can get that job done.”

As part of the diplomatic process, Ashton will go to Tehran on March 9-10.

A diplomatic source clarified that the two sides did not produce a text of an agreed framework for future negotiations or detailed agenda for upcoming meetings, rather only agreeing a broad range of subjects to be addressed in coming months.

While modest in scope, the arrangement is an early step forward in the elusive search for a settlement that could ward off the danger of a wider war in the Middle East, reshape the regional power balance and open up big new trade opportunities with Iran, an oil-producing market of 76 million people.

The Vienna talks followed a ground-breaking interim accord between Iran and the six powers in November under which Tehran suspended higher-level enrichment until late July in return for limited relief from sanctions.

That deal was made possible by the election of relative moderate President Hassan Rouhani, replacing bellicose hardliner Mahmoud Ahmadinejad, last year on a platform of rebuilding the OPEC member state’s foreign relations.

The UN nuclear watchdog, which has a critical role in monitoring the agreement’s implementation, issued an update on Thursday showing Iran was living up to its commitments.

Its report said Iran’s most sensitive nuclear stockpile — uranium refined to a fissile concentration of 20 percent, a relatively short technical step away from potential weapons-grade material — had declined significantly for the first time in four years and was now well below the amount needed for one bomb, if processed to a high degree.

But many difficult hurdles remain to be settled.

Iran’s unfinished heavy water Arak reactor, which could yield plutonium for bombs, and its underground Fordow uranium enrichment site will be among key sticking points in the talks.