Republican presidential nominee Donald Trump states that he believes U.S. President Barack Obama was born in the United States at a campaign event at the Trump International Hotel in Washington, D.C., U.S., September 16, 2016. REUTERS/Mike Segar

U.S. Democratic presidential candidate Hillary Clinton leaves after speaking at the Black Women's Agenda Annual Symposium in Washington, U.S., September 16, 2016. REUTERS/Carlos Barria

Republican presidential nominee Donald Trump's campaign plane (L) sits on the same tarmac as Democratic nominee Hillary Clinton's campaign plane (R), at Washington National airport in Washington, U.S., September 16, 2016. REUTERS/Carlos Barria

U.S. Democratic presidential candidate Hillary Clinton leaves after speaking at the Black Women's Agenda Annual Symposium in Washington, U.S., September 16, 2016. REUTERS/Carlos Barria

Republican presidential nominee Donald Trump's campaign plane (R) sits on the same tarmac as Democratic nominee Hillary Clinton's campaign plane (L), at Ronald Reagan Washington National Airport in Washington, U.S., September 16, 2016. REUTERS/Carlos Barria

A still image taken on September 7, 2016 from a video posted on social media said to be shot in Aleppo's Al Sukari on September 6, 2016, shows a boy breathing with an oxygen mask inside a hospital, after a suspected chlorine gas attack, Syria. Social Media via Reuters/File Photo TV

The logo of Swiss drugmaker Novartis is seen at its headquarters in Basel, Switzerland October 22, 2013. REUTERS/Arnd Wiegmann/File Photo

Lauri Love reacts as he arrives for his extradition hearing at Westminster Magistrates' Court in London, Britain September 16, 2016. REUTERS/Peter Nicholls