Obama meeting with hostile foreign leaders is a necessary step in proving that we are still a world power. This is a bit of a gamble, because he has historically been very soft in relations with hostile leaders. I hope he exhibits poise and respect to them, and I also hope he can be frank and firm, to show them that the United States is still respectable on the world stage.
Hostility doesn't just end by people not talking to one another. It could well be a strategy that doesn't work out, at a certain point if somebody doesn't want to hear you then there's nothing you can do about it, but the potential here is very high and the risk is relatively low.
As we have seen over the last decade, war is expensive and sometimes unnecessary. We have gone to war for accusations that have been unfounded. It was better that we take steps to ensure war can be avoided and peace can be achieved. Obviously, these meetings do not guarantee anything. However, the attempt to prevent hostile engagements is a much better prospect than war.