After a two-hour breakfast with Putin, Mr. Obama sat down with CBS News.
"I think this is a very smart, very tough, very unsentimental person," Mr. Obama said.
Despite that less than warm personal assessment, the president said they're mostly on the same page on some vital issues.
"I don't think that the Russians want to see Iran possessing a nuclear weapon," he said.
White House advisers say Mr. Obama repeatedly brought up the danger of a nuclear Iran in private meetings, urging Russian leaders to take the threat more seriously. He has made the same case for North Korea, which this weekend launched another round of threatening test missile flights.
"Do you worry about the possibility of war with North Korea? How close are we?" Reid asked the president.
"I don't think that any war is imminent with North Korea," Mr. Obama said. "I think they understand that they would be overwhelmed in a serious military conflict with the United States."
The centerpiece of this U.S.-Russia summit is a provisional agreement to reduce the two nation's nuclear arsenals by as much as a third, signed by President Obama and Russian President Dmitri Medvedev. Mr. Obama calls it leading by example.
"Once you do that, then you've got an international community that is collectively focused on the issue," he said. "So that when we approach North Korea or Iran, it is as a united front."
The president also prodded this government-controlled nation to become more Democratic. In a speech today, he said governments that serve their own people survive; those that serve their own power do not.