Christopher Johnston is a fellow at Georgetown University's Institute for the Study of Diplomacy and a graduate of the Royal Military College, Duntroon.

Officials are hailing an interim agreement to halt or reverse key aspects of the Iranian nuclear program. Negotiations have concluded with unusual speed, amid some goodwill on both sides. In addition to the main conference, Iranian officials have met separately with their American counterparts in bilateral meetings. Such rare encounters follow the historic telephone call in September between Presidents Rouhani and Obama, the first of its kind in three decades.

Diplomacy – backed with the credible threat of violence – might just bear fruit, but only if this agreement is followed with strict verification. As was recently noted by Dina Esfandiary, one nation has more to fear than most.

Israel was not privy to the discussions in Geneva, and may yet decide to strike Iran’s nuclear program on its own. 'Ahmadinejad was a wolf in wolf’s clothing. Rouhani is a wolf in sheep’s clothing', said Prime Minister Netanyahu last month. 'Israel will not allow Iran to get nuclear weapons. If Israel is forced to stand alone, Israel will stand alone.'

Prime Minister Netanyahu is not the only one unwilling to risk rapprochement between the US and Iran.

Members of Congress have placed stringent conditions on any sanctions relief, including the admonition that Iran must cease uranium enrichment in all forms. That is clearly not the outcome in Geneva, and the Obama Administration is generally maladroit in dealing with the legislative branch.

So this agreement will be tough to ratify and tricky to implement, yet all sides have an interest in sustaining momentum. Once the excitement of this deal gives way to frustration, symbolic steps will prove valuable.

One such step would be for Iran to initiate a dialogue with Israel. There have been encouraging signs in this direction. Last month Rouhani cancelled an anti-Israel conference in Tehran. Prime Minister Netanyahu has indicated he would be amenable to a telephone call from President Rouhani. As head of the Likud party, Netanyahu is probably the only Israeli politician with enough authority and conservative support to successfully parley with Iran.

Any such telephone call would certainly be met with a frosty reception in Jerusalem. That does not mean the gesture is without value. At the very least, some conciliation towards Israel would ease the passage of sanctions relief through the US Congress.

There is no ‘Track II’ dialogue between these two enemies, no backchannel or trusted intermediary to prevent the unintended lurch to war. Quite rightly, Israel judges Iranian intentions on the basis of Tehran's inflammatory rhetoric. An Iranian diplomatic overture towards Israel would be a meaningful gesture once the hard work of implementation gets underway.