JOHN NEGROPONTE

Thomas-Greenfield joined the State Department more than three decades ago, when Black women were even more of a rarity in the U.S. diplomatic corps than they are today. That makes her the most experienced diplomat of the six people named by Biden for top national security positions on Monday. Her tenure at the State Department rivals that of previous U.N. ambassadors like Richard Holbrooke, John Negroponte and Thomas Pickering, all of them white men. Other than secretary of state, the U.S. ambassador to the United Nations is often the most high-profile foreign policy portfolio in a presidential administration. Thomas-Greenfield's immediate predecessors — all women — highlight that dichotomy: Rice, Samantha Power, Nikki Haley and Kelly Craft.

The White House could use a stronger nuclear deal with Iran as a way to proceed with North Korea, John Negroponte, former U.S. ambassador to the United Nations, told CNBC on Monday. "We've got to improve the Iran agreement to the point where it's also something that could serve as a model for North Korea. "We have to think about triangulating between Iran and North Korea," Negroponte added in a "Squawk Box " interview. However, that summit was cut short after Trump announced a deal could not be reached. The White House was pushing for North Korea to give up its nuclear weapons for an economic boost.