After three rounds of talks in less than two months, Iran and six world powers have reached a preliminary agreement in Geneva on curbing Tehran's nuclear programme in exchange for some sanctions relief. The breakthrough came amid a history of failed negotiations, and could be the first step towards a detente between Western powers and Iran after 35 years of hostility. Noticeably, the agreement came less than three months after Iran's new President Hassan Rouhani committed to changing Iran's relationship with the world.

The deal will have immediate regional and international ramifications, and once a long term deal is reached, possibly within a few months, rapprochement between Washington and Tehran is likely to pave the way towards major realignment in the greater Middle East region.

It's also expected to open the way towards the recognition of Iran's regional role starting with Syria, Iraq, the Gulf region, and eventually in Afghanistan.

As the US downsizes its overall military presence, it expects the Iranian leadership to be less of a nuisance and more cooperative towards crisis management in the greater Middle East.

And it seems, many in Tehran, and among its supporters, are pleased to see Iran replace Saudi Arabia or Israel as a reliable intermediary for the United States in the region.

Some argue that this is all wishful thinking and will prove short-lived considering the decades' long antagonism and ideological differences. Others argue that in the long term, Iran (and Turkey) could prove more useful as US clients/partners than Israel and Saudi Arabia, considering their regional weight and historic importance.

The new deal will have serious ramifications on at least seven regional fronts:

Iran

The Islamic Republic is at the heart of any future regional shifts of power. US failures in Afghanistan, and more importantly in Iraq and Syria, have already strengthened Iran's hand. And the newly gained confidence in Tehran will be further enhanced by the removal of economic sanctions, and buttressed by a bigger role in a weakened region.

Question: How will Iran's rehabilitation and opening to the West affect the balance of power within the country and the future of the mullahs' rule?

Syria

Iran's expected participation in the Geneva-2 negotiation over Syria's future is its first reward for “good behaviour”. A staunch supporter of Bashar al-Assad, with its special forces fighting alongside his regime, Tehran is likely to ensure Assad's survival, and along with Russia, assist in his rehabilitation as an acceptable regional leader. Tehran and Moscow are eager to end the war and shift the emphasis from ousting Assad to “fighting terrorism” in Syria.

Question: What does a greater Iranian role in Syria mean to the struggle of Syrians for freedom from dictatorship, and the outcome of the horrific civil war there?

Iraq

The country is in a quagmire 10 years after the military invasion. It's terribly polarised between Sunni and Shia forces and hundreds - even thousands - of people are killed every month by suicide bombings. Tehran exercises major influence in the country, over Nouri al-Maliki's government, and among the Shia majority. And as of late, the authoritarian Maliki has emerged as an indispensable link between Tehran and Washington as he spearheads the fight against “extremist Sunni groups”.

Question: Considering its new vigour, will Iran's support for Maliki lead him to an even greater monopoly of power and deeper divisions in the country?

Saudi Arabia

The wars in Iraq, Syria and the conflict in Lebanon - in addition to the upheaval of the predominantly Shia majority in Bahrain - have deepened the rift between Riyadh and Tehran. Judging from criticism made recently by Saudi intelligence chief Bandar bin Sultan, who is Washington's ally in the Kingdom, the Saudi leadership is the most alarmed with the potential US-Iran detente and the rise of an unrestrained Iran on the Middle East stage. Further, Saudi-Iranian antagonism will lead to major sectarian escalation with incalculable price for the region.

Question: Will the hardening theological triangle - Saudi, Iran and Israel - take the region to new historic lows as the danger of sectarian conflict looms large in the region?

Afghanistan

As the US withdraws/redeploys outside the country in 2014 - after a 13 year war - leaving behind only residual forces through 2024, Washington can use all the help it can get to maintain control. With a certain influence over Afghanistan's northern regions, Tehran could be of assistance if it chooses to help stabilise Afghanistan and deter the return of the Taliban.

Question: Having briefly helped US forces fight against the Taliban after 2001, will Tehran cooperate once again with the US?

Palestine/Lebanon

Palestine is a domestic redline for both Washington and Tehran and, therefore, expect little or no change to the occupation of Palestine where they've agreed to disagree. Tehran has already lost much influence among the Islamist Palestinian factions due to its support of the Assad regime; its only influence remains with Hezbollah.

Question: Will Iran's Lebanese ally emerge stronger or weaker from the Syrian civil war, and will it become a Lebanese, and not an Israeli menace?

Israel

For the foreseeable future, Israel will continue to be the only nuclear power in the region. But Israel is no less annoyed by a resurgent Iran than it is by its nuclear development, especially the fact that Tehran has already acquired the nuclear know-how. Some suggest that this could lead to new unspoken Israeli alliance with the so-called moderate Sunni regimes, ie, Saudi Arabia, UAE, Jordan, Egypt, against their common nemesis, Iran.

Question: Since Israel is particularly eager for such an arrangement, will such alliances finally see the light of day and what repercussion will that have on the region?

Marwan Bishara is the senior political analyst at Al Jazeera.