U.S. Commerce Secretary Wilbur Ross has at the last minute pulled out of a trip to Germany on Tuesday, the German economy ministry said, not giving a reason for the cancellation which comes at a time of friction with Washington over trade policy.

He had been due to meet German Economy Minister Brigitte Zypries and to address an event hosted by the economic council of Chancellor Angela Merkel's conservative party.

Trade has turned into a contentious issue between Germany and the United States under U.S. President Donald Trump, who advocates more protectionist policies while Germany has made free and fair trade one of its priorities in its Group of 20 presidency.

Merkel, who will host a G-20 summit in Hamburg on July 7-8, said late on Monday she did not see common interests between the United States and Europe on climate and trade policy at the moment.

The United States could be relied on when it came to security and Berlin was looking to see where there were other areas of agreement, said Merkel.

"But on the issue of climate protection or free trade, we do not have this at the moment," she said, adding that Trump had a vision of globalization "that is different to mine — very much so."

Last week, Merkel used an appearance alongside veteran German-born U.S. diplomat Henry Kissinger to stress that the transatlantic relationship was rooted in "joint convictions, values, and understandings."

A strong European economy is good for the United States, she said, less than a month after Trump called Germany's trade and spending policies "very bad." Merkel is seeking re-election for a fourth term in September.