"The guy's known for saying some pretty, pretty unconstructive stuff, how's that? And offensive stuff. So, I don't take that seriously," the president said.
Obama had considerable praise for his Russian counterpart and said that over the year of negotiations over the nuclear treaty, "he has consistently been able to keep the commitments that he's made, and follow through on them, and the treaty that we signed today is just one example of that."
Asked if he was convinced that Medvedev was in charge in Russia, as opposed to powerful former president and now-Prime Minister Vladimir Putin, Obama said that Medvedev "takes the counsel of Putin very seriously.
"You know, Russia is a big, complicated country just like the United States is," he said. "And there are all sorts of different voices coming at him at any given time that he's got to take into account."
Concerning Afghan President Hamid Karzai's recent outbursts about the U.S. influence over his country, Obama notably did not call Karzai an "ally" but did stress that he is and will be a "partner" to the United States.
Asked if he was "convinced" that Karzai is committed to making the necessary adjustments and changes to give his government greater legitimacy, Obama said, "I think he is committed to doing that."
"But that doesn't mean that it's easy," he noted. "And that doesn't mean that there aren't going to be times when he and I disagree in terms of how things should proceed, and how rapidly things should proceed."
Obama said that in his conversations with Karzai, the Afghan leader has responded to suggestions of what can help him achieve a "strong, stable and prosperous Afghanistan."
"The key is to continue to have those frank and honest conversations in a way that allows that strategic partnership to develop, and grow so that we can succeed," the president said. "Again, primarily from our perspective, because it's national for our national security."