President Donald Trump's recent comments and angry tweets about Germany's "unfair" trade practices could leave the U.S. as the odd man out in the global economy.

Fresh from a meeting in Brussels with the leaders of the Group of Seven largest economies, Trump fired yet another tweet salvo at a longtime U.S. ally, sharply attacking Germany's trade and spending policies.

"We have a MASSIVE trade deficit with Germany, plus they pay FAR LESS than they should on NATO & military. Very bad for U.S. This will change," the president said.

The tweet follows a series of summit meetings with European leaders that reportedly included similar complaints about Germany's trade policy and NATO contributions. The president's stance drew a sharp response from German Chancellor Angela Merkel, who voiced doubts about the reliability of the United States as an ally.

"Recent days have shown me that the times when we could rely completely on others are over to a certain extent," Merkel said Monday in a speech in Berlin. "Europe must take its fate into its own hands."