Turkish Prime Minister Binali Yildirim (R)speaks next to US Vice President Joe Biden (L) during a joint press conference following their meeting on August 24, 2016 at the Cankaya Palace in Ankara. US Vice President Joe Biden on August 24, 2016 said Washington had made clear that pro-Kurdish forces in Syria must not to cross west of the Euphrates River, a prospect alarming for Turkey. His comments come after Turkish troops launched an operation inside Syria to cleanse the key town of Jarabulus from Islamic State (IS) jihadists. / AFP PHOTO / ADEM ALTANADEM ALTAN/AFP/Getty Images

Turkish Prime Minister Binali Yildirim (R)and US Vice President Joe Biden (L) hold a joint press conference following their meeting on August 24, 2016 at the Cankaya Palace in Ankara. US Vice President Joe Biden on August 24, 2016 said Washington had made clear that pro-Kurdish forces in Syria must not to cross west of the Euphrates River, a prospect alarming for Turkey. His comments come after Turkish troops launched an operation inside Syria to cleanse the key town of Jarabulus from Islamic State (IS) jihadists. / AFP PHOTO / ADEM ALTANADEM ALTAN/AFP/Getty Images

Turkish Prime Minister Binali Yildirim (R) and US Vice President Joe Biden (L) hold a joint press conference following their meeting on August 24, 2016 at the Cankaya Palace in Ankara. US Vice President Joe Biden on August 24, 2016 said Washington had made clear that pro-Kurdish forces in Syria must not to cross west of the Euphrates River, a prospect alarming for Turkey. His comments come after Turkish troops launched an operation inside Syria to cleanse the key town of Jarabulus from Islamic State (IS) jihadists. / AFP PHOTO / ADEM ALTANADEM ALTAN/AFP/Getty Images

U.S. Senator Carl Levin (D-MI) departs following the weekly Democratic caucus policy luncheon at the U.S. Capitol in Washington June 24, 2014. REUTERS/Jonathan Ernst/File Photo

(From L) Turkish Prime Minister Binali Yildirim (L), US Vice President Joe Biden (C) and Turkish Foreign Minister Mevlut Cavusoglu (R) walk at Cankaya Palace in Ankara, on August 24, 2016. US Vice President Joe Biden arrived in Ankara to meet Erdogan, with agreeing a unified strategy on Syria set to be a crucial issue. Biden is likely to face expressions of alarm from Turkey about the activities inside Syria of the People's Protection Units (YPG) militia, which Washington sees as an ally but Ankara regards as a terror group. / AFP PHOTO / TURKISH PRIME MINISTRE PRESS OFFICE / HAKAN GOKTEPE / RESTRICTED TO EDITORIAL USE - MANDATORY CREDIT "AFP PHOTO / TURKISH PRIME MINISTER PRESS OFFICE / HAKAN GOKTEPE" - NO MARKETING - NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS HAKAN GOKTEPE/AFP/Getty Images

Turkish Prime Minister Binali Yildirim (R) shakes hands with US Vice President Joe Biden (L) before their meeting at Cankaya Palace in Ankara, on August 24, 2016. US Vice President Joe Biden arrived in Ankara to meet Erdogan, with agreeing a unified strategy on Syria set to be a crucial issue. Biden is likely to face expressions of alarm from Turkey about the activities inside Syria of the People's Protection Units (YPG) militia, which Washington sees as an ally but Ankara regards as a terror group. / AFP PHOTO / TURKISH PRIME MINISTRE PRESS OFFICE / HO / RESTRICTED TO EDITORIAL USE - MANDATORY CREDIT "AFP PHOTO / TURKISH PRIME MINISTER PRESS OFFICE / HAKAN GOKTEPE" - NO MARKETING - NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS HO/AFP/Getty Images

Turkish Prime Minister Binali Yildirim (R) talks with US Vice President Joe Biden (L) at Cankaya Palace in Ankara, on August 24, 2016. US Vice President Joe Biden arrived in Ankara to meet Erdogan, with agreeing a unified strategy on Syria set to be a crucial issue. Biden is likely to face expressions of alarm from Turkey about the activities inside Syria of the People's Protection Units (YPG) militia, which Washington sees as an ally but Ankara regards as a terror group. / AFP PHOTO / TURKISH PRIME MINISTRE PRESS OFFICE / HO / RESTRICTED TO EDITORIAL USE - MANDATORY CREDIT "AFP PHOTO / TURKISH PRIME MINISTER PRESS OFFICE / HAKAN GOKTEPE" - NO MARKETING - NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS HO/AFP/Getty Images

Turkish Prime Minister Binali Yildirim (R) shakes hands with US Vice President Joe Biden (L) at Cankaya Palace in Ankara, on August 24, 2016. US Vice President Joe Biden arrived in Ankara to meet Erdogan, with agreeing a unified strategy on Syria set to be a crucial issue. Biden is likely to face expressions of alarm from Turkey about the activities inside Syria of the People's Protection Units (YPG) militia, which Washington sees as an ally but Ankara regards as a terror group. / AFP PHOTO / TURKISH PRIME MINISTRE PRESS OFFICE / HO / RESTRICTED TO EDITORIAL USE - MANDATORY CREDIT "AFP PHOTO / TURKISH PRIME MINISTER PRESS OFFICE / HAKAN GOKTEPE" - NO MARKETING - NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS HO/AFP/Getty Images