The US president also said he hoped that Trump would not simply take a realpolitik approach in cutting deals and doing "whatever's convenient at the time."

Merkel thanked Obama for the "excellent cooperation" and praised him as a reliable partner in difficult times.

She expressed her gratitude for a close, trusting and friendly cooperation over the eight-year term he served.

The Chancellor said she would "do everything possible to work well with the newly-elected president."

Obama also thanked Merkel for Germany's contribution to the fight against the Islamic State (IS) and to the Syrian conflict.

In an interview with German broadcaster ARD and German weekly news magazine Der Spiegel, Obama had previously warned of growing political tensions in industrialized countries.

"If the global economy does not react to people who feel left behind when inequality continues to grow, we will see the split in the industrialized countries expand," Obama was quoted as saying.

Obama and Merkel will meet with French President Francois Hollande, British Prime Minister Theresa May, Spanish Prime Minister Mariano Rajoy and Italian Prime Minister Matteo Renzi on Friday in Berlin to exchange views on the future of the Ukraine crisis, the future approach towards Russia, the civil war in Syria and the fight against IS.