(Photo: Reuters)

At what is likely to be the German leader's final visit to the White House before she retires from politics, Biden praised Merkel's "exemplary life of groundbreaking service to Germany and ... to the world".

Biden reiterated his concerns about the Nord Stream 2 pipeline being built under the Baltic Sea from Russia to Germany but said he and Merkel were united in their belief that Russia should not use energy as a geopolitical weapon.

Washington and Berlin also have differing views on doing business with China, but both leaders said they would stand up for democratic principles and universal rights when they saw any country working to undermine them.