President Donald Trump has said Germany owes Nato "vast sums of money" and should pay the United States more for defending it.
He made the statement in a series of tweets from his Mar-a-Lago base in Florida on Saturday morning.
Mr Trump, after a video appeared to show him ignoring Ms Merkel's request to shake hands at a photo opportunity, said: "Despite what you have heard from the FAKE NEWS, I had a GREAT meeting with German Chancellor Angela Merkel.
"Nevertheless, Germany owes vast sums of money to NATO & the United States must be paid more for the powerful, and very expensive, defense it provides to Germany!"
The US has some 35,000 service personnel stationed in Germany, according to US military figures.
Prior to his inauguration, Mr Trump declared Nato "obsolete" but has since modified his stance, telling European leaders the alliance remains of strategic importance.