Prime Minister Ahmet Davutoğlu and German Chancellor Angela Merkel discussed the Turkey-EU relations prior to Sunday's summit in a phone call on late Friday.
According to the prime ministry sources, the two leaders agreed to work on developing the cooperation and relations between Turkey and the European Union in the summit of European Union leaders and Turkish officials which will took place on Sunday.
Davutoğlu and Merkel also exchanged ideas over the refugee crisis as roughly a million refugees and migrants fleeing war and deprivation in the Middle East, Africa and Asia are expected to arrive in Germany this year alone.
Merkel wants a multi-pronged solution to the crisis, centered on working with other EU countries and Turkey. Others in her ruling coalition want to cap Germany's refugee intake.
European and Turkish officials are working to smooth out their remaining differences on an agreement to help stem flows of migrants to Europe, which they hope will be signed on Sunday.
German government sources said they were optimistic an action plan could be agreed with Turkey and signed at Sunday's summit.