Bernie Sanders criticized fellow Democratic presidential candidate Hillary Clinton on NBC's "Meet the Press" Sunday, saying unlike her, President Obama has been right on relations with Iran.

The Vermont senator called out foreign policy comments Clinton made in 2007 during the early stages of competing against then-Illinois Sen. Barack Obama for the party's nomination.

"A question was asked to Obama. They said 'would you sit down and talk to the Iranians?' He said 'yeah, I would.' Point being that you talk to your adversaries, you don't run away from them. Secretary Clinton I think called him naive. Turns out Obama was right," Sanders told host Chuck Todd Sunday.

Despite the difference in diplomatic approaches, Obama appointed Clinton to secretary of state one year later during his first term as president.

Sanders did not comment on Clinton's performance as top diplomat, but called the International Atomic Energy Agency's approval of Iran's nuclear weapons clean-out a "huge step forward." He added there are still considerable concerns about Iran's nuclear weapons program.

Clinton and Sanders will meet tonight again for the third Democratic debate, set to be broadcast on NBC.