How many demons must President Obama exorcise as he leads the US response to the catastrophe in Haiti? Demons, to be sure, of past neglect alternated with bouts of heavy-handed intervention.

And there is a view that another demon belongs in the pack as well: that of his predecessor's response to hurricane Katrina.

To lay the ghosts of New Orleans, Mr Obama has to show himself concerned, up-to-date with what is happening on the ground, competent, and in command. Everything that George Bush so patently was not.

Yet, except in the broadest category of competence, Katrina is a distraction here. It is not just that an earthquake and a hurricane are different things, or that New Orleans was a first-world city in an advanced country, while Port-au-Prince most definitely was not. It is that New Orleans was unambiguously a US responsibility.

Part of the delay in co-ordinating emergency help might have stemmed from disagreements and misunderstandings between the state and federal authorities. But Katrina presented the distressing spectacle of a national government comprehensively failing its own citizens in their hour of need in the most elementary way.

Not only the logistics were at fault, but the appraisal of what was required; indeed, the understanding that there were any people, let alone tens of thousands, in desperate need at all. This was an emergency response that seemed to sum up in all sorts of ways the failings of George Bush's presidency. If a state cannot provide the most basic assistance to its own disaster-victims not two hours' flying time from the capital, what use is the state at all?

The task facing Mr Obama and his administration in dispatching aid to Haiti, beyond trying to project concern and competence, is quite different. In some ways, it is almost the opposite. In New Orleans, the US administration had a responsibility to take charge – and for too long, lamentably, did not do so. In Haiti – unless Mr Obama's United States wants to be in the business of colonisation and coups – it must avoid conspicuously throwing its weight about, or any appearance of trying to grab control.

The US administration's words and deeds since the earthquake, and most particularly Hillary Clinton's brief trip to Port-au-Prince, have provided a compelling study in post-Bush US diplomacy. The US may be sending troops – 3,000 initially, with another 7,000 committed, which makes the total akin to the whole British contingent in Basra – but this is an exercise that tests the practical limits of the sort of "soft" power Mr Obama favours.

First, the US is stressing that this is an emergency relief operation, not a move with any ulterior motive, such as extending US political or military sway. Mrs Clinton's official plane doubled as an aid-transport; on its return journey it evacuated US nationals.

Second, there has been a deliberate attempt to avoid any proprietorial inferences. The President, his spokespeople and above all his Secretary of State have been at pains to treat Haiti as a sovereign state, albeit one desperately weakened by catastrophe. Mrs Clinton made a point of meeting President Preval and his Prime Minister, in line with diplomatic protocol. And there was a joint US-Haiti communiqué.

The message was that the US wanted to support what remained of Haiti's always fragile state structures, not to undermine them. Both Mr Obama and Mrs Clinton have also used every opportunity to state their respect for the leading role of the United Nations in the relief operation. They appreciate, and are careful of, international precedence.

And third, the US is keeping a low national profile. There is no boastful show of Stars and Stripes; the US is projecting itself to Haiti and to the world, as one part, albeit a large and significant part, of a co-operative endeavour.

The difficulty is that appearance and reality conflict. The US is not only the closest developed state to Haiti, but probably the only one anywhere with the capacity to deliver relief on the scale required here. One of its first moves was to take control of the airport – prompting charges that US flights were being given precedence.

But few countries have the capacity to move so quickly, and the airport had to be secured and made operational as an absolute priority. As its troop numbers increases, the US will find it ever harder to claim that it is just another benevolent contributor.

What the US does or does not do in Haiti will not determine the reputation of Barack Obama's presidency at home, as Katrina coloured the second term of George Bush. But it will directly affect US relations with Haiti in coming years and convey a message about US intentions around the world. So far, Mr Obama, with the able support of Mrs Clinton, has tiptoed as delicately around the eggshells as it was possible to do. It will only become more difficult from now on.

_Independent