Apart from Mr Khattar, the state's Agriculture Minister Om Parkash Dhankar also congratulated Kovind, an official release said.
Earlier today, BJP had named Dalit leader and Bihar Governor Ram Nath Kovind as the NDA candidate for the top post.
Mr Kovind, who is a Dalit, is a farmer's son and his humble origins and simple lifestyle is being stressed by BJP leaders.
He was named Governor of Bihar by the centre three years ago. He is a former leader of the BJP's unit that represents Dalit and served two terms as a member of the Rajya Sabha. He is a trained lawyer who has appeared at the High Court and Supreme Court.
By selecting a Dalit, the BJP has moved to consolidate its support among lower castes and poorer voters.