LONDON — Much of the world’s attention at the Group of 20 economic summit on Friday and Saturday will be on President Trump’s first meeting with his Russian counterpart, Vladimir V. Putin, with strenuous efforts to decipher the nature of the long-distance bromance between them.

But the leader of the world’s other superpower, Xi Jinping of China, will also be in Hamburg, Germany, ready to slip quietly into the widening gap between Mr. Trump and longtime European allies and to position Beijing as the globe’s newest, biggest defender of a multilateral, rules-based system.

Mr. Xi will have just concluded a state visit with Germany, including bilateral meetings and a small dinner Tuesday night in Berlin with the summit host, Chancellor Angela Merkel, who has made no secret of her differences with Mr. Trump.

Having helped Ms. Merkel open the Berlin Zoo’s new $10 million panda garden (complete with two new Chinese pandas), and watched a German-Chinese youth soccer match, Mr. Xi will have already made a mark.