Even before Facebook’s Sheryl Sandberg urged women to “lean in” as a workplace strategy, the L-word had already begun to take hold in US foreign policy circles. Proponents of robust American engagement call for the Obama administration to “lean forward”; critics say it has been too happy to “lean back and wait”.

President Barack Obama’s eagerness to lean back from some of the Middle East’s many problems is easy to understand, even if it is not accepted by everyone. Given the complexity of the civil war in Syria, he is right to worry that the US could be sucked into an endless conflict if it gets more involved. And with all sides in Egypt’s struggle denouncing American interference, a low profile makes some sense at the moment.

But there is one looming question where the US cannot afford to take such a back-seat approach: Iran’s nuclear programme.

Together with the other major powers, the US is expected to resume talks in September with Tehran at a time when the negotiations are reaching a crucial point. Iran’s nuclear facilities have been inching forward while the negotiations have stalled. At the same time, the surprise election in June of Hassan Rohani as Iran’s next president– after a campaign in which he criticised the Iranian government’s negotiating stance – has created what many observers feel to be the best potential opening since 2009. As a result, there is a now-or-never feel to the next few months’ diplomacy.

Yet so far the response in Washington to Iran’s political earthquake has been to sit back and wait. “The onus is on Iran,” a US official said last week, talking about the prospect of Washington putting forward a new negotiating offer that might be more attractive to Tehran. “We are waiting for a serious proposal back.”

Washington’s caution is partly down to well-based concerns about overreacting to the Iranian election. Mr Rohani has not yet even taken office, let alone appointed his own negotiating team to take over from Saeed Jalili, the conservative official who was also a presidential candidate.

The broader message from the election is also uncertain. Mr Rohani clearly benefited from discontent at an economy hit hard by international sanctions, but before the vote few would have identified him as a reformer. And while Mr Rohani has emphasised his strong relationship with the Ayatollah Ali Khamenei, it is still not clear if the supreme leader will give him any leeway in the nuclear talks. For US officials, the election has produced more questions than answers.

Yet despite all that, there are still strong reasons for the US to take the initiative – if not offering immediate sanctions relief, then at least providing more assurances about how sanctions might be withdrawn in the event of progress in the talks.

While the US would be wise to avoid the game of courting particular Iranian factions, it makes sense to show greater willingness to engage with Mr Rohani. The new Iranian president will be better placed to resist domestic pressure for him not to make any concessions if he can point to a constructive approach from Washington.

The Obama administration also needs to build a stronger political case at home for what it hopes to achieve in the talks. Congress, where scepticism about Iranian intentions is bipartisan and sky-high, is considering new sanctions on Iran’s oil trade that would wreak further damage on its economy. If the administration takes a back seat, it could find itself implementing new sanctions that undermine Mr Rohani at the very moment he is taking office.

Most of all, negotiations are a chance to test the other side. Iran’s election may be confusing but it did appear to reflect deep-seated weariness at international isolation and the sanctions this has produced. There is only one way for the US to find out if the political landscape really has changed in Tehran.

Worried about political attacks from the right, Mr Obama adopted a highly cautious approach to talks with Iran during last year’s re-election campaign while Iran’s own presidential politics put the negotiations on hold for the first half of this year. The next few months could provide a defining moment in Iran’s nuclear programme – but not if Mr Obama decides to lean back and wait.

Get alerts on Barack Obama when a new story is published

Copyright The Financial Times Limited 2019. All rights reserved.

Follow the topics in this article