The next six months will be key for the potential rapprochement between Iran and the West, after Tehran agreed a nuclear deal with the P5+1 world powers in Geneva.

US President Barack Obama said the agreement is “an important first step toward a comprehensive solution”, with much of the sanctions built up against Iran over recent years remaining unchanged.

The agreement sets out a six-month period for the two sides to build on the momentum coming out of Geneva and restore some of the trust lost amid decades of strained relations between Tehran and Washington.

“This is only the first step,” said Iran’s Foreign Minister Mohammad Javad Zarif, at a press conference at the Geneva meetings. “We need to start moving in the direction of restoring confidence, a direction in which we have managed to move against in the past.”

The Princeton-based American Iranian Council (AIC) welcomed the agreement, with its president, Hooshand Amirahmadi, expressing his “heartfelt support for the nuclear breakthrough, the unravelling of the communication taboo and the opening for a broader reconciliation between the US and Iran”.

“The deal signed in Geneva is a first step toward, hopefully, a comprehensive deal that will be signed at the end of the six-month confidence-building period,” the AIC said.

As part of the agreement, the P5+1 countries – the US, the UK, France, China, Russia and Germany – have imposed limits on Iran’s nuclear programme over the next six months, which must be complied with before economic sanctions against the Islamic Republic can be relaxed further.

Tehran has committed to halting uranium enrichment above 5 per cent and dismantling technical connections required to enrich to above 5 per cent – the level required for weapons-grade material. It has also committed to neutralising its stockpile of near-20-per-cent pure uranium by diluting it to below 5 per cent or by converting the stockpile to a form not suitable for further enrichment.

At the same time, Iran must halt progress on enrichment capacity and, crucially, has committed to no further advances at the Arak heavy-water reactor. The status of the facility was reported to be a key reason why the initial Geneva talks earlier in November broke down, with France expressing concern about the facility and its potential capability to produce weapons-grade plutonium.

“Arak has elicited particular alarm because it could be eventually used to produce plutonium and provide Iran with a second path to a nuclear weapon,” Barclays Capital analyst Helima Croft said in a recent research note. “Moreover, once it becomes operational in the summer of 2014, it will be difficult for outside powers to use military force to disable the facility without triggering very adverse environmental consequences.”

Perhaps the greatest test for Iran over the next six months will be allowing the level of transparency demanded by the P5+1, an issue that damaged the trust between the US and the Islamic Republic in previous negotiations.

In the conditions agreed upon, the International Atomic Energy Agency (IAEA) must be allowed daily access to Natanz and Fordow. Iran started to build the underground Fordow plant in secret more than five years ago near the city of Qom, before it was discovered by Western intelligence services in 2009.

The IAEA must also be allowed access to design information for the Arak reactor and more frequent inspector access to the site.

In return, Tehran will receive some relief from the international sanctions that have been strengthened considerably over the past two years, with the White House specifying that this relief would be limited, temporary and reversible.

Tehran is set to receive as much as $7bn over the next six months from the relief of economic sanctions, including $4.2bn in frozen assets.

“If Iran does not fully meet its commitments during this six-month phase, we will turn off the relief and ratchet up the pressure,” said President Obama.

Not all world powers welcomed the deal. The negotiations have been viewed with caution elsewhere in the Middle East, with Israel and Saudi Arabia, Washington’s long-standing allies in the region, doubting Tehran’s commitment to peaceful nuclear advancement.

“Israel cannot participate in the international celebration, which is based on Iranian deception and (international) self-delusion,” said Yuval Steinitz, Israel’s cabinet minister for intelligence issues.

He added that the deal was more likely to bring Iran closer to developing a bomb.