"Yes, he will drop by on the way to Berlin," Kremlin spokesman Dmitry Peskov was quoted as saying by Russia's Ria Novosti news agency.
He was referring to Mr Putin's talks with German Chancellor Angela Merkel.
Ms Kneissl, 53, will marry businessman Wolfgang Meilinger at vineyard in Austria's Styria state, reports say.
Meanwhile, Mr Putin's adviser Yuri Ushakov told Russia's Interfax news agency: "We will call in and congratulate them."
He added that the Russian president had been invited to attend the wedding when he visited Austria earlier this year.
Ms Kneissl, an independent, was picked for the foreign minister job by Austria's far-right Freedom Party - a coalition partner in the current government.
The Freedom Party is believed to have links to Russia's governing United Russia party.
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