U.S. prosecutors have launched a money-laundering investigation of a member of Vladimir Putin’s inner circle, several people familiar with the efforts said, in a politically sensitive escalation of pressure on the Russian president’s cadre of billionaire supporters.

The U.S. Attorney’s Office for the Eastern District of New York, aided by the Justice Department, is investigating whether Gennady Timchenko transferred funds linked to allegedly corrupt deals in Russia through the U.S. financial system, the people said.

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