Merkel has been an outstanding partner says Obama

US President Barack Obama lauded German Chancellor Angela Merkel on Thursday as an "outstanding" international partner who showed a recognition that being a good leader also meant engaging with the world.

"All I can say is that Chancellor Merkel has been an outstanding partner, and Chancellor Merkel is perhaps the only leader left among our closest allies that was there when I arrived," he said, after talks with Merkel in his farewell tour of Europe.

While acknowledging that they have not always been on the same page every issue, he cited Merkel's "integrity, her truthfulness, her thoughtfulness" among traits he appreciated.

"Her commitment to looking out for the interests of the German people first, but recognising that part of good leadership on behalf of the nation requires engaging the world as a whole... I think she's been outstanding."

In a ringing endorsement of Merkel before she announces if she would stand for a fourth term in next year's elections, Obama said: "It's up to her whether she wants to stand again... But if I were here and I were German and I had a vote, I might support her."

Obama acknowledged that Merkel will have big international burdens to shoulder if she decides to run again.

"I wish I could be there to lighten her load. But she's tough," he added.