In breaking news this morning, the US administration announced the lifting of some long-standing sanctions on Cuba: Cuban-Americans are to be allowed to travel there and send money to relatives and American telecommunications firms will be allowed to apply for licenses to operate in Cuba.

This is a modest step, in line with Barack Obama’s campaign promises.

Travel to Cuba by other Americans will remain illegal, and, as the BBC reports, “there is no talk for the moment of opening diplomatic relations or of lifting the general trade embargo”.

Nonetheless, on an issue where politicians have traditionally tried to outdo one another in hardline measures to appeal to the Cuban exile community, any movement forward is significant. The administration has left the door open to further liberalisation if it is met by a favorable response from Cuba and the Cuban government in turn has expressed a readiness to negotiate without preconditions.

It’s hardly surprising that the policy of sanctions against Cuba has been a failure; indeed, it’s hard to point to any cases where sanctions have succeeded. From League of Nations sanctions against Mussolini, right down to current measures against Hamas, Iran and North Korea, sanctions have generally been ineffective at best and often counter-productive.

Twenty years ago, when the Soviet empire entered meltdown, it was reasonable to expect that Cuba would go the same way as the other satellite states. The fact that it has not — that Bulgaria, for example, is now a functioning democracy, while the Castros still rule the roost in Cuba — no doubt has many causes, but an important one must be the ready availability of the US and its sanctions as a scapegoat for the regime’s failings.

If sanctions are going to work at all, they usually work fairly quickly; the idea of sanctions that last for decades is nonsensical. But another problem with sanctions is that they are often easier to impose than to end.

There is a fairly general recognition among the American political class that policy on Cuba has been a failure. Prominent Republican Senator Richard Lugar summed it up earlier this year: “By directing policy toward an unlikely scenario of a short-term democratic transition on the island and rejecting most tools of diplomatic engagement, the US is left as a powerless bystander, watching events unfold at a distance”.

Once sanctions are in place, however, any move to end them looks like a concession of weakness and an undeserved bonus to the target government.

Obama’s problem is to find a convincing way out of this impasse.