Obama denies $400M payment to Iran was ransom
The payment was part of a decades-old dispute over a failed military equipment deal dating to the 1970s, before the Islamic revolution in 1979.
Obama also answered political questions at the news conference, pushing back at Republican presidential nominee Donald Trump's suggestions that the November election might be rigged, calling the assertion "ridiculous."
The president's appearance before reporters followed an hours-long meeting with military leaders at the Pentagon on the fight against the Islamic State group.
Obama said there have been gains in weakening IS in Iraq and Syria, but he conceded the extremist group still poses a threat to the United States as it shifts its tactics to carrying out attacks elsewhere around the world.
On Iran, Obama expressed surprise at criticism of his administration's cash payment to settle a longstanding legal claim, adamantly rejecting claims that it was a ransom paid for the release of the four Americans.