Khan made the comments while addressing a special session of the 'Azad Jammu and Kashmir' Legislative Assembly in Muzaffarabad as Pakistan marked its Independence Day "in solidarity with Kashmiris".
"I believe it is a (huge) strategic blunder by Modi. It will cost Modi and his BJP government heavily. I consider it a big miscalculation by Modi. He has played his final card," Khan said.
Vowing to take the Kashmir cause forward, the Pakistan Tehreek-e-Insaf (PTI) chief said: "I'll become the voice for Kashmir. I will be Kashmir's ambassador."
He said it was a challenging task to draw attention of world leaders to the "human rights violations in occupied Kashmir", Geo News reported.
"But now, the Kashmir issue is under the spotlight of (world media). By (clamping down further) on occupied Kashmir, Modi has in fact helped to internationalize the dispute," said the cricketer-turned-politician.
The Pakistan government earlier decided to observe their Independence Day in solidarity with "the brave Kashmiris and their just struggle for their right of self-determination".
India's Independence Day on Thursday will be observed as "Black Day" across Pakistan.
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