Obama also strongly rejected Republican accusations that his administration deliberately leaked classified information about a cyberattack on Iran's nuclear centrifuge program.

CNN: Obama, GOP and economic blame game

In recent months, Iran has begun installing hundreds of more advanced centrifuge machines at nuclear sites, which are capable of producing fuel at three times the current rate, according to U.S. and U.N. officials.

WSJ: Kerry Focuses on Iran, North Korea Leaders

North Korea could provide Iran with a range of supplies for its nuclear program, including uranium ore, centrifuge machines and enriched uranium, according to these officials.

WSJ: Iran-North Korea Pact Draws Concern