Asked about the vulnerability of Iran's nuclear installations, he told CNN: "Well, they certainly can be bombed. The level of effect would vary with who it is that carries it out, what ordnance they have, and what capability they can bring to bear."
Iran maintains its nuclear programme is for peaceful purposes, but the United States and other Western nations fear Tehran wants to acquire nuclear weapons.
Israel has called Iran's nuclear programme the major threat facing its nation. Gen Petraeus declined to comment about Israel's military capabilities, according to CNN.
Iran had until the end of last year to accept a deal offered five permanent UN Security Council members – Britain, China, France, Russia and the United States, plus Germany.
It did not do so. Instead, Tehran gave the West until the end of January to accept its own proposal.
Petraeus said he thought there was still time for the nations to engage Iran in diplomacy, noting there is no deadline on the enactment of any US contingency plans.
But he added that "there's a period of time, certainly, before all this might come to a head".