Im not sure how much power Obama really would have in this situation. The US can put pressure on Israel to halt and bring about peace talks. This is what Obama wants to do. Obviously there wont be real peace, but a decreased amount of violence at least.
It seems that both Israel and Hamas are really stepping up. Obama has a lot on his plate unfortunately. He is not able to succeed in everything, for he is only a man. What is happening in the Middle East is interesting. Perhaps this is just part of the usual cycle of violence, but it will be very interesting if it proves to be something more.