Kullu (Himachal Pradesh), Aug 31 - Holding on to the belief that his son is alive, an anxious father has hired a private rescue team but wants Indian authorities to extensively search for the 24-year-old Israeli-American backpacker who went missing July 21.

Amichai, who also served in the Israeli army for three years, went missing while trekking in Himachal Pradesh's picturesque Parbati valley in Kullu district, about 300 km from the state capital Shimla, said his father Jacob Shtainmetz.

Amichai had gone for trekking along with his friend but took a different route on the way back - and hasn't been seen since.

'We want extensive search of the entire trek (that my son had taken) by Indian authorities... I believe he is still alive and trapped in high mountain passes. Unless extensive search is carried out, it's difficult for him to return safely,' Shtainmetz said.

'Our own efforts have borne no fruit so far.'

The private rescue team he has hired with the help of the Israeli embassy has been on the job since Amichai's disappearance.

'He is very sturdy and well built. He can survive without having food for days together even in extreme conditions,' the father, who has announced a reward of Rs.100,000 for anyone giving clues about his missing son, said.

According to Superintendent of Police (Kullu) K.