By any measure, this was a big week for diplomacy at the United Nations. Barack Obama started it off by delivering an important and potentially far-reaching speech reflecting on the challenges America faces in attempting to protect its core interests and project its values in a rapidly changing and dangerous world.

The complicating factor in all of this, according to the president, is what he recognises as the limits of American power to provide solutions to many of the complex problems we currently face.

The week came to an end with upbeat reports from the P5 + 1 talks on Iran’s nuclear programme and word that the Security Council had passed a measure pressing Syrian compliance with their agreement to surrender their chemical weapons’ stockpile.

Mr Obama’s Tuesday speech to the General Assembly set the tone for the week.

It deserves to be read in its entirety since it represents the most thoughtful statement to date of the president’s reflections on how protecting America’s interests and realising its aspirations must be tempered by an recognition of the limits of America’s power.

A few writers saw the speech as an effort to craft an “Obama Doctrine”. In fact, it was anything but a new “doctrine”. Instead of framing hard fast answers, the president asked tough questions.

It was a humble speech. It recognised that force cannot always advance progress in democratisation, that we live in a world of “imperfect choices” and “unintended consequences” that must always be factored into any discussion of the use of forces and that after more than a decade or war, Americans have developed a “hard earned humility” regarding foreign interventions.

The speech, however, was not a pacifist manifesto since Mr Obama acknowledged that even with these complicating considerations, there were still times when America would need to act in defence of its core interests, or to stop a humanitarian catastrophe. And there would be times when the “credible threat of force” might be required to transform a situation or avert a crisis.

But there was more to the week than a speech, no matter how instructive it may have been.

Throughout the past several days the US and Iran flirted with each other, sending repeated positive signals about their commitment to turn a page to work to address concerns relating to Iran’s nuclear programme.

Analysts and commentators looking for a quick hit story were initially disappointed with the failure of the two leaders to meet or to provide them with a photo of a handshake.

But the disappointment was cast aside on Friday with news of the week culminating with a late-Friday surprise phone call between presidents Obama and Rouhani in which it was reported that the two leaders agreed to focus their efforts on not only the nuclear issue, but on other regional matters – most notably achieving a negotiated settlement to the conflict in Syria.

The news about progress on a Security Council resolution on the Syria front is also important.

The US and its allies may have wanted the resolution to be tougher and to say and do more to punish the Assad regime. But given the realities of the Council, the fact that a consensus was reached is itself important.

To have moved in just a few weeks’ time from a war footing to constructive engagement on two explosive issues has to be seen as a “good week”.

There were, to be sure, critics who responded in full force. President Obama’s speech was denounced as a muddled celebration of weakness, and a surrender of leadership.

The Security Council resolution on Syria was dismissed as toothless, since it did not include an enforcement mechanism. The outreach to Iran was derided as naïve and dangerous. And there were those who suggested that credit for the week should not go to Mr Obama, but to prime minister Putin and president Rouhani.

But the critics are wrong. There is no shame in Mr Obama recognising and seizing on an opening that provided the possibility of doing a good thing.

Credit, of course, must also be given to the Iranian and Russian leaders. But there can be no denying that Mr Obama, by not behaving as George Bush might have, was able to wring the best out of what was a bad situation. He was able to replace hollow boasting and absolutist proclamations, with a commitment to dialogue based on mutual respect and put us on the path to the resolution of some (not all) problems, without risking involvement in a destabilising new war.

The test of how successful this week has been will come as we move forward.

If Syrian disarmament proceeds apace, if the resolution of the chemical weapons issue moves us closer to a Geneva Summit and if the slight thaw with Iran promotes serious progress on addressing their nuclear programme – then this will be remembered as a very good week, indeed.