Why does India resist third-party mediation on the Kashmir issue?

There is no real pressure on India to address the dispute because we are securing from Pakistan what we want through other means

The question is thrown up because of an exchange, minor and casual for the United States but apparently vital and embarrassing to India, between US President Donald Trump and Pakistani leader Imran Khan. Mr Trump’s comment was: “I was with Prime Minister (Narendra) Modi two weeks ago. We talked about this subject and he actually said: ‘Would you like be a mediator or arbitrator?’ I said: ‘Where?’ He said: ‘Kashmir’.’
 
This is quite specific and unambiguous. The obvious thing for India to do, assuming Mr Modi did not in fact say this, or even if he said it differently,