Mary Dejevsky: Less of the professor and more of the fighter, Mr Obama

He has an excellent case to make for each controversial decision

There are times when you don't know whether to laugh or to cry – in foreign policy as in so much else. Only three months ago, Barack Obama was being taken to task by his own disillusioned voters for not supporting Iran's election protests more vigorously. Now, more predictably, he is taking flak from the right.

But what is striking, and perhaps ominous, for Obama is the similar nature of the complaints. Why, asked his supporters, had he not come out immediately, all – metaphorical – guns blazing, against what was so obviously a stolen election? Small matter that Tehran's streets remained volatile and the extent of election fraud was far from demonstrated, Mr Obama was denounced as something akin to a class traitor.

Nor did the criticism stop there. Members of his erstwhile fan club discerned a pattern of caution and weakness that cast Obama as a follower rather than a leader, uncertain in his response to unforeseen events. They seemed to forget that one reason for his victory – and probably why they themselves had voted for him – was the considered nuance that he promised to bring to the White House, compared with the knee-jerk zeal of George Bush. But that is by the by.

Now, as the UN General Assembly convenes in New York, the US right has picked up the chorus of "weak and ineffectual" leadership. The immediate pretext was Obama's reversal of the Bush decision to site missile defence installations in Central Europe. Republican politicians and publicists, elated to have found a cause, took turns to condemn Obama for "selling out" the national interest, betraying the heroic Czechs and Poles, and giving Russia a "veto" over US policy.

It was not long before they added to their charge sheet George Mitchell's admission of failure in his latest effort to broker a resumption of peace talks in the Middle East. Or before they remembered Obama's rather mild objection – he called it "a mistake" – to Scotland's release of the convicted Lockerbie bomber. So it is that, as Obama prepares to address the UN General Assembly tomorrow, he must contend with a hail of verbal arrows threatening to pierce his international authority at home.

Viewed from this side of the Atlantic, what is more surprising than the mounting criticism of Obama on foreign policy – that happens to any president, and the vicious healthcare debate means that Republicans are in the market for anything that will diminish Obama's stature – is the President's calm and collected responses. Given that the electoral cycle in the US moves faster than it does here, however, and that public patience – like the average attention span – is shorter, might it not be time for Obama to show a more combative side? His demeanour on his record talk-show blitz last weekend was described by some as almost professorial.

It is not as though he does not have an excellent case to make for each of his supposedly controversial decisions. The Iranian election may have been rigged, but perhaps not to the point where the result was a complete travesty. To have spoken out too soon might have encouraged further pointless confrontation. It could also have risked pushing either President Ahmadinejad or the ayatollahs, or both, into a corner at the very time the question of Iran's nuclear ambitions was coming to a head. As it is, Iran is returning to the negotiating table and the supreme leader, Ayatollah Khomeini, has just reiterated that Iran has no plans to develop nuclear weapons. Is that such a bad result?

Some, including nationalistic Russians and fearful Central Europeans, might interpret Obama's missile defence decision as a retreat. It is not; but even if it were, it would be a "smart" retreat that reflects multiple US interests. It removes at a stroke the biggest block to better relations with Russia; it signals to the Czechs and everyone else that the US is no longer in the business of dividing Europe into "old" and "new"; it signals a changed – and less alarming – US assessment of the potential threat from Iran; and it will save the US a great deal of money on technology that is still unproven. What's not to like?

As for the Middle East, Obama has been in office for only eight months, and the Israeli government for only five. It is only nine months since Gaza was in flames. As with Iran, patience is an essential, and underestimated, virtue.

Like Bill Clinton in his time, Obama is guaranteed a rapturous reception when he stands up to address the UN tomorrow. Since January, he has transformed the image of the US abroad and, with it, the international diplomatic climate. But like Bill Clinton, he had better watch his back. Friends abroad, however numerous and enthusiastic, are no substitute for political allies at home.

m.dejevsky@independent.co.uk