John Kerry (center) stands with other military personnel in an unspecified location circa the 1960s. The details of Kerry's service during the Vietnam War, and his subsequent anti-war activism, became the focus of a veterans' group's smear campaign against him during his 2004 presidential campaign. Kerry Campaign/Getty Images hide caption
President Biden is welcomed by Rep. Jim Clyburn, D-S.C. on Jan. 27, 2024, as he campaigned ahead of the South Carolina Democratic primary. Kent Nishimura/AFP via Getty Images hide caption
John Kerry says "we can win this fight" against climate change. Sean Gallup/Getty Images hide caption
John Podesta looks on during a meeting between President Biden and mayors at the White House on Jan. 19, 2024. Brendan Smialowski/AFP via Getty Images hide caption
Climate envoys John Kerry of the U.S. and Xie Zhenhua of China met in California in November. As the world's two-largest greenhouse gas emitters, agreement between the two countries is considered key for significant developments at the UN climate summit. William Vasta/The Annenberg Foundation Trust at Sunnylands hide caption
Chris Gloninger, pictured in June 2022. Chris Gloninger hide caption
In this photo provided by the U.S. Department of State, U.S. Special Presidential Envoy for Climate John Kerry attends a meeting with Chinese Foreign Minister Wang Yi via video link in Tianjin, China, Wednesday, Sept. 1, 2021. Wang warned Kerry on Wednesday that deteriorating U.S.-China relations could undermine cooperation between the two on climate change. AP hide caption
Kerry gets interviewed by NPR's Lucian Kim on Wednesday at Spaso House, the official Moscow residence of the U.S. ambassador to Russia. Stefan Mizha/U.S. Embassy Moscow Press Office hide caption
Former Secretary of State, John Kerry poses on Martha's Vineyard in Vineyard Haven, Mass., on Sept. 18, 2020. Erin Clark/Boston Globe via Getty Images hide caption
U.S. Secretary of State John Kerry attends the peace conference in Paris on Sunday. Foreign ministers and representatives from about 70 countries are seeking to revive the moribund Israeli-Palestinian peace process. Bertrand Guay/AFP/Getty Images hide caption
Russian Foreign Minister Sergey Lavrov (left) and U.S. Secretary of State John Kerry (right) enter a news conference room Friday in Geneva to announce a cease-fire agreement for Syria. Fabrice Coffrini/AFP/Getty Images hide caption
British Chancellor of the Exchequer George Osborne, the United Kingdom's head financial official, leaves after making a statement at the Treasury in London on Monday. Stefan Rousseau/AFP/Getty Images hide caption
U.S. Secretary of State John Kerry (right), along with British Foreign Secretary Philip Hammond (left), speak to reporters in London on May 12. They tried to assure European banks they won't be penalized for conducting legitimate business with Iran. Critics say it should not be up to the U.S. to encourage investment in Iran. Josh Lederman/AP hide caption
Secretary of State John Kerry pauses during his remarks about seeing the Hiroshima Peace Memorial Park and Museum, the site of the 1945 atomic bombing, during a news conference at the conclusion of the G-7 Foreign Ministers' Meetings in Hiroshima on Monday. Jonathan Ernst/AFP/Getty Images hide caption
Sec. State John Kerry spoke with NPR's Steve Inskeep at the State Department. Kainaz Amaria/NPR hide caption
Secretary of State John Kerry spoke with NPR's Steve Inskeep at the State Department. Kerry said if Congress or a future president reverses a nuclear control agreement with Iran, U.S. credibility will suffer. Kainaz Amaria/NPR hide caption
U.S. Secretary of State John Kerry (left) and Saudi Foreign Minister Adel al-Jubeir held a joint news conference Thursday in Riyadh, Saudi Arabia. Andrew Harnik/AP hide caption
U.S. Secretary of State John Kerry speaks at a news conference in Sharm el-Sheikh, Egypt, on Saturday. Kerry said he's returning to nuclear negotiations with Iran with "important gaps" standing in the way of a deal. Brian Snyder/AP hide caption
Senate intelligence committee chairwoman Sen. Dianne Feinstein, D-Calif., is again defending her report on CIA torture methods, which was set to be released this week. J. Scott Applewhite/AP hide caption
At a Cairo aid conference to help rebuild Gaza, Secretary of State John Kerry paused to rub his eyes Sunday. The U.S. is promising another $212 million in aid. Carolyn Kaster/AP hide caption
Egyptian President Abdel-Fattah el-Sissi and U.S. Secretary of State John Kerry talk before a meeting at the Presidential Palace on Sunday in Cairo. Brendan Smialowski/AFP/Getty Images hide caption
Russian Foreign Minister Sergei Lavrov, left, and U.S. Secretary of State John Kerry before their talks Friday in London. Afterward, they reported no breakthroughs on finding a solution to the crisis in Ukraine. Brendan Smialowski/AP hide caption