Foreign Minister Sushma Swaraj has been deputed to stand in for Modi and pledge New Delhi's strong support at the Kathmandu meet, the official told ET.

Even as Nepal tried hard to host Modi, for the third time in one year, even for less than 24-hours, the PM decided to continue with his pre-scheduled engagement of launch of three major new initiatives 'Smart Cities Mission', 'Atal Mission for Rejuvenation and Urban Transformation' (AMRUT) and the 'Housing for All' initiative, officials said.

The conclave in Delhi will be attended by Ambassadors of 15 countries, including those of the US, Japan, Germany, Canada, France, Sweden and Russia, which have shown interest in building smart cities in India besides providing other urban solutions. Also present at the meet will be elected mayors and chairpersons of 500 corporations and municipalities from across the country.

Explaining the decision, an official said, "The 'Smart City' initiative and sprucing up Indian urban centres top the PM's priorities and the June 25 event was a prescheduled one."

A senior Nepalese government official told ET, "The Nepalese government was extremely keen to host PM Modi as a special guest for the donors' meet. He had informed our leadership that he will certainly nominate a senior minister in case he is unable to attend the meet."

Swaraj, on her return from New York where she participated at the International Yoga Day at the UN, will head towards Kathmandu and is expected to announce hefty aid for the reconstruction of the country, which was ravaged by a 7.8-magnitude quake in April.

Nepal is a foreign policy priority for the Modi regime, officials said, adding that India and Japan are planning to co-host a follow up donors' conference.

Both Delhi and Tokyo were earlier keen to host the first donors' meet but Kathmandu turned down the offer on the ground that through this meet the government wants to boost confidence of the locals and once again showcase the country as a tourist destination.

India was the first to reach aid to Nepal after the quake. Japan, on the other hand, possesses world-class expertise in post-quake reconstruction activities.

While Nepal invited Chinese Premier Li Keqiang through the Chinese mission in Kathmandu, Beijing is expected to depute a senior leader for the meet. Foreign Minister Wang Yi could represent China at the meet, according to media reports.

Nepal has estimated that it would require nearly $7 billion towards reconstruction and rehabilitation. It had shared its estimate with India when its Finance Minister, Ram Sharan Mahat, visited Delhi to invite Modi for the June 25 meet. This was followed by an informal visit by Nepal's Planning Minister, Bimalendra Nidhi, to Delhi to meet Swaraj and other Indian officials last week.