Vali Nasr, an Iranian-American academic, is serving as senior adviser to Richard Holbrooke, the US special representative for Afghanistan and Pakistan.
|Key US allies, such as Egypt, have accused Hezbollah of meddling in their internal affairs [GETTY]
A professor of International Politics at the Fletcher School of Law and Diplomacy and senior fellow at the Council on Foreign Relations, Nasr is best known for his work on Iran and Sunni-Shia tensions in the Middle East.
In a videotaped appeal in March, Barack Obama, the US president offered a "new beginning" in US-Iranian relations, calling for renewed exchanges and greater partnership. Iranian officials said action was needed to repair the relationship, but welcomed his words.
Here, Nasr talks to Al Jazeera about Obama's overtures to Tehran and increasing tension between some Arab states and Hezbollah ahead of crucial elections in Iran and Lebanon.
Al Jazeera: Barack Obama, the US president, has reached out to Iran. Will Iran respond in kind?
Nasr: President Obama's policy is a clear departure from that of the Bush administration in that it is serious about engagement with Iran.
Iranian leaders have been used to dealing with the Bush administration that spoke of engagement but was not serious about.
In addition, President Obama enjoys great popularity around the world and even in the Muslim world.
This means that the context for US-Iran relations has radically changed, and that forces Iranian leaders to reassess their policies and goals. I think Iranian leaders are debating how to respond to the Obama administration.
A clear direction will not likely emerge until the presidential elections in June decide the shape of the Iranian government.
Officials of Washington's Arab allies have been warning that Iran's influence in the region is as dangerous to them as its nuclear programme; is this because of a perceived Sunni-Shia rivalry?
The Shia-Sunni rivalry is real. We can see that it has not finished in Iraq. Sectarian violence is making a comeback and even when there was relative calm still the two sides were not reconciled to peace.
Sectarian tensions are also simmering just below the surface in Lebanon and we have seen flare-ups in Bahrain and Saudi Arabia over the course of the past year.
Many of these tensions have local roots, and not everywhere will they break out into larger conflicts. But what makes them more important is that they fit into the larger power rivalry in the region between Iran and its Arab neighbours.
When you have a larger rivalry in a region then smaller conflicts find greater meaning and can be related to one another to impact the outcome of that larger conflict.
In the Middle East, the Shia communities look to Iran as ally, patron and source of support, and Arab rulers have supported Sunni forces opposed to Shia empowerment. So long as the Iranian-Arab rivalry for domination of the Middle East continues, sectarian tensions will continue to have larger geo-strategic significance.
Benyamin Netanyahu, the new Israeli prime minister, is more concerned about the Iran situation than about dealing with the Palestinians. Is Iran a threat?
Iran threatens different countries in different ways. Countries around the Gulf rim fear Iranian hegemony. They fear Iran will dictate terms to them or may encourage their Shia populations into rebellion.
|Nasr: A nuclear Iran could change the balance of military and political power in the region
In the Levant, Egypt and Jordan do not fear direct exercise of Iranian power, but are worried about the implications of Iranian interference in issues that they have traditionally held control over, such as the Palestinian issue or Lebanon.
Israel fears a nuclear Iran, not only because Iran may actually use a nuclear weapon against Israel, but also because it will change the balance of military and political power in the region.
In reality Iran's military is not big enough or well-equipped enough to threaten any country. But Iran has done well in using non-state actors like Hamas and Hezbollah to project power, and has been very effective in wooing the Arab street.
If nuclear capability were to be added to the mix then Iran's influence will be even greater. What matters at this stage is that the Arab world and Israel are worried about what a more influential Iran will mean, and in politics perceptions matter.
Will Tehran open up to the international community in the event that Mahmoud Ahmadinejad, the Iranian president, is not re-elected in June?
President Ahmadinejad has been a divisive figure both inside Iran and internationally. Outside Iran he enjoys great popularity in the Arab world, but has a very negative image in the West.
A new face at the top in Tehran will clearly present fresh opportunities for dialogue and diplomacy even if the positions of various sides do not change fundamentally.
The Lebanese parliamentary elections will be held in June. Seen as a battleground for regional influence, Saudi Arabia and Iran are arming their Lebanese allies with campaign money. Votes are being bought with cash or in-kind services. How important is Lebanon to Iran?
Lebanon is clearly important to Iran only because Hezbollah is important to Iran.
Hezbollah continues to be Iran's only success since 1979 in exporting its revolution to the Arab world. Iran cannot afford (especially now that it is trying to expand its influence in the region) to let Hezbollah lose ground in Lebanon.
There are also strong personal and religious ties between Hezbollah and various powerful elite and organisations in Iran, which means that there are many times that Hezbollah can lobby in Tehran for support and policy.
Iran would also like to use a victory in Lebanon as leverage both against Israel and Syria, as well as by defeating Saudi-backed forces in Lebanon establish that it now is in the driver seat in deciding the direction of Lebanese politics. That would give Iran more leverage in dealing with the US.
What are the regional repercussions should Hezbollah win the elections?
It will underscore two things. First, that non-state actors, equipped with a radical message and rejecting any engagement with Israel enjoy political momentum; and second that Iran has made effective inroads into Arab politics, and that in an important Arab country that was where Arab world fought its own struggles for power in the 1980s now Iran is the more important outside actor.
Several weeks after Egyptian security forces uncovered a Hezbollah cell allegedly planning to carry out attacks in the country, Hosni Mubarak, the Egyptian president, warned "regional forces" against interfering with his country.
Hezbollah is interested in Gaza, and to have sustained access to Gaza, especially to fund and arm Hamas, Hezbollah needs to have a nucleus of operations in Egypt. Iran's interest is not operational, but much broader, it is strategic.
Iran is now competing with leaders in the Arab world for control of the Palestinian issue, and has used the Gaza war to weaken rivals in Arab capitals.
During the war Iranian press attacked Egypt far more often and more forcefully at times than they criticised Israel. Egypt is a recognised leader of the Arab world and hence Iranian interest in undermining its stance on the Palestinian issue.