The Kremlin said it would consider the invitation. U.S. Secretary of State Marco Rubio has said he hopes Putin will attend, giving him a chance to meet President Donald Trump and other leaders.
Tusk said Russia might interpret an invitation as encouragement to continue its aggressive policy. His warning reflects the risk that a high-profile diplomatic meeting could be seen as acceptance of the status quo, even if its stated purpose is dialogue.
The G20 summit is scheduled for December in Miami, Florida. Tusk made the comments at a news conference in Warsaw on Thursday.