Greeting world leaders this week in western Russia, President Vladimir V. Putin has rolled out a red-carpet welcome in his pursuit of partners, like China and Iran, interested in ending U.S. dominance over the international financial system.

But one guest among the dozens of leaders present was not like the others.

President Recep Tayyip Erdogan of Turkey, who arrived in the Russian city of Kazan on Wednesday, was the only leader of a NATO country to take part in the meetings, known as the BRICS summit.

He addressed Mr. Putin as his “dear friend,” a term of endearment he has used repeatedly for the Russian leader and a sign of Mr. Erdogan’s longstanding effort to position Turkey as a critical player in a world of rivals — to the occasional frustration of his NATO allies.

Mr. Erdogan’s visit was also a feather in Mr. Putin’s cap, analysts said, as he seeks to prove that he is far from the global pariah the West has tried to make him into since he launched Russia’s full-scale invasion of Ukraine in 2022.

Mr. Putin asserted on Wednesday that a shift toward “a multipolar world order” had already begun, saying that an “irreversible process” was underway.

NATO is vilified in Russia and by many BRICS members, whose leaders frequently criticize the alliance. (BRICS stands for the group’s founding members, Brazil, Russia, India, China and South Africa.) To have Mr. Erdogan, the leader of a longtime NATO member country, express interest in closer relations with the growing bloc underscored the widening circle Mr. Putin is trying to gather around himself, experts said.