Many view the agreement world powers have sealed with Iran as a sensation. DW's Rob Mudge says it's too soon to be jubilant. Above all, the ball is in the US court.
These days, the term "historic" is used too frequently, and quite prematurely. This is certainly true for the outcome of the nuclear talks between the West and Iran. What has now been achieved in Geneva can at best be called a small step in the right direction - nothing more, nothing less. Secret US-Iran talks held parallel to the official negotiations have certainly shown that the Americans are still the first and most important contact for the leadership in Tehran.
Barack Obama must take advantage of this edge in credibility - this is where the actual work for his government begins. If he wants to turn this small step into a sustainable result, he'll now have to tackle domestic and foreign policy constraints.
On the one hand, he faces a hostile Congress at home in Washington, where many refuse rapprochement while demanding tougher sanctions on Iran. They argue that Iran hasn't proven itself particularly reliable in the past, and that this time too Tehran will try to find a loophole. On the other side, we have the powerful energy sector and the US trade giants chomping at the bit to return to Iran and embrace their business interests once more. Obama must give them guarantees that they will be the ones to sign lucrative deals with Iran, not the Europeans.
In the foreign policy arena, the US President must appease Israel, his most important partner in the region. He must try to prevent complete meltdown in a relationship that is already shaken. Israel made it clear ahead of the agreement that it will not accept any deal or rapprochement with Iran - and it has threatened to react accordingly. Obama will have to muster every ounce of his diplomatic skills to appease Israel and to convince Benjamin Netanyahu's government that approaching Iran is in the interest of all the players in the region.
The progress made in Geneva is likely to strain relations between the US and Saudi Arabia as well. Iran is the Riyadh royal family's worst regional enemy, not least because it supports the Syrian regime and has close ties to Hezbollah. There is some concern that the US rapprochement with Iran could come at the expense of Saudi Arabia's security.
It will be a tightrope act for Obama, as he tries to reassure his regional partners while not compromising the subtle progress with Iran.
The European allies should also not be forgotten - above all the French. The bilateral talks between Washington and Tehran came as a surprise to the French government. Paris was so displeased that it scuttled a possible breakthrough in the first round of talks. Again, regional interests are at stake - of course, Europeans also want a slice of the expected lucrative oil and gas contracts. Obama must try to carry the Europeans with him - not an easy task in view of the Americans' tarnished credibility in the wake of the NSA eavesdropping scandal.
Should Obama manage to turn this preliminary deal into a long-term agreement with Iran, it could be a signal for the entire region and, in the long run, it could even lead to a solution in the Mideast conflict. That would be a task for Obama's successor. And only then will we able to speak of a truly historic moment.