The Pope has been involved in sensitive negotiations about the future of the Catholic Church in the country as he seeks to bring an end to persecution of Chinese Catholics.
While Tibetans uphold the Dalai Lama as their spiritual leader, China views him as a dangerous separatist so the Pope's exclusion of him from the summit in Italy has been perceived by some as an attempt to curry their favour.
The conference aims to recreate a day of prayer which Pope John Paul II initiated 30 years ago - an event that the Dalai Lama was invited to at the time.
This year, it will be held on 20 September in Assisi but the Dalai Lama's secretary has confirmed that, this time, he has not received an invitation.
It's not the first time that the Dalai Lama has been snubbed by the Pope.
In 2014, Pope Francis also refused to meet him when he attended a meeting of Nobel peace prize winners in Rome.
Peter Smith, a Catholic commentator, told Premier: "I wouldn't see this as being a permanent snub but probably just one where he doesn't see it quite so opportune in the next couple of months to worsen the situation by inviting the Dalai Lama along.
"There are 9 million Catholics in China and I understand that Pope Francis is negotiating with the Chinese government over improved access to churches and maybe he just doesn't want to do anything to jeopordise those negotiations at the moment"
By Dan Golding