US Secretary of State John Kerry (L) gestures as he speaks while he arrives with Russian Minister for Foreign Affairs Sergei Lavrov (R) prior to a meeting to discuss the Syrian crisis on September 9, 2016, in Geneva. The United States and Russia will make a fresh bid to end the bloodshed in Syria on September 9, 2016 as Moscow-backed regime forces make new advances against rebel fighters on the ground. US Secretary of State John Kerry flew into Geneva for crunch talks with his Russian counterpart Sergei Lavrov, with Washington warning talks could not go on forever without a breakthrough. The two powers back opposite sides in the five-year conflict, with Moscow supporting the regime of President Bashar al-Assad and the US behind the rebels. / AFP PHOTO / POOL / KEVIN LAMARQUEKEVIN LAMARQUE/AFP/Getty Images

US Secretary of State John Kerry (L) and Russian Minister for Foreign Affairs Sergei Lavrov (R) take their seats for a meeting to discuss the Syrian crisis on September 9, 2016, in Geneva. The United States and Russia will make a fresh bid to end the bloodshed in Syria on September 9, 2016 as Moscow-backed regime forces make new advances against rebel fighters on the ground. US Secretary of State John Kerry flew into Geneva for crunch talks with his Russian counterpart Sergei Lavrov, with Washington warning talks could not go on forever without a breakthrough. The two powers back opposite sides in the five-year conflict, with Moscow supporting the regime of President Bashar al-Assad and the US behind the rebels. / AFP PHOTO / POOL / KEVIN LAMARQUEKEVIN LAMARQUE/AFP/Getty Images

US Secretary of State John Kerry (L) and Russian Minister for Foreign Affairs Sergei Lavrov (R) speak as they arrive prior to a meeting to discuss the Syrian crisis on September 9, 2016, in Geneva. The United States and Russia will make a fresh bid to end the bloodshed in Syria on September 9, 2016 as Moscow-backed regime forces make new advances against rebel fighters on the ground. US Secretary of State John Kerry flew into Geneva for crunch talks with his Russian counterpart Sergei Lavrov, with Washington warning talks could not go on forever without a breakthrough. The two powers back opposite sides in the five-year conflict, with Moscow supporting the regime of President Bashar al-Assad and the US behind the rebels. / AFP PHOTO / POOL / KEVIN LAMARQUEKEVIN LAMARQUE/AFP/Getty Images

US Secretary of State John Kerry (L) and Russian Minister for Foreign Affairs Sergei Lavrov (R) looks on prior to a meeting to discuss the Syrian crisis on September 9, 2016, in Geneva. The United States and Russia will make a fresh bid to end the bloodshed in Syria on September 9, 2016 as Moscow-backed regime forces make new advances against rebel fighters on the ground. US Secretary of State John Kerry flew into Geneva for crunch talks with his Russian counterpart Sergei Lavrov, with Washington warning talks could not go on forever without a breakthrough. The two powers back opposite sides in the five-year conflict, with Moscow supporting the regime of President Bashar al-Assad and the US behind the rebels. / AFP PHOTO / POOL / KEVIN LAMARQUEKEVIN LAMARQUE/AFP/Getty Images

US Secretary of State John Kerry (L) and Russian Minister for Foreign Affairs Sergei Lavrov (R) looks on prior to a meeting to discuss the Syrian crisis on September 9, 2016, in Geneva. The United States and Russia will make a fresh bid to end the bloodshed in Syria on September 9, 2016 as Moscow-backed regime forces make new advances against rebel fighters on the ground. US Secretary of State John Kerry flew into Geneva for crunch talks with his Russian counterpart Sergei Lavrov, with Washington warning talks could not go on forever without a breakthrough. The two powers back opposite sides in the five-year conflict, with Moscow supporting the regime of President Bashar al-Assad and the US behind the rebels. / AFP PHOTO / POOL / KEVIN LAMARQUEKEVIN LAMARQUE/AFP/Getty Images

US Secretary of State John Kerry (L) and Russian Minister for Foreign Affairs Sergei Lavrov (R) looks on prior to a meeting to discuss the Syrian crisis on September 9, 2016, in Geneva. The United States and Russia will make a fresh bid to end the bloodshed in Syria on September 9, 2016 as Moscow-backed regime forces make new advances against rebel fighters on the ground. US Secretary of State John Kerry flew into Geneva for crunch talks with his Russian counterpart Sergei Lavrov, with Washington warning talks could not go on forever without a breakthrough. The two powers back opposite sides in the five-year conflict, with Moscow supporting the regime of President Bashar al-Assad and the US behind the rebels. / AFP PHOTO / POOL / KEVIN LAMARQUEKEVIN LAMARQUE/AFP/Getty Images

US President Barack Obama disembarks from Air Force One upon arrival at Andrews Air Force Base in Maryland, September 9, 2016, as he returns to Washington from a 9-day trip to Nevada, Hawaii, Midway Island, China and Laos. / AFP PHOTO / SAUL LOEBSAUL LOEB/AFP/Getty Images

US President Barack Obama disembarks from Air Force One upon arrival at Andrews Air Force Base in Maryland, September 9, 2016, as he returns to Washington from a 9-day trip to Nevada, Hawaii, Midway Island, China and Laos. / AFP PHOTO / SAUL LOEBSAUL LOEB/AFP/Getty Images