Prime Minister Imran Khan on Saturday formally inaugurated the historic corridor to facilitate visa-free entry of Indian Sikh pilgrims to one of Sikhism's holiest shrines in Pakistani town of Narowal.

The US "welcomes the opening of a new border crossing" between India and Pakistan, "the Kartarpur corridor," US State Department Spokesperson Morgan Ortagus said in a video posted on her official twitter handle.

The newly opened corridor is a step towards promoting greater religious freedom," she said.

Ortagus also sent her best wishes to the pilgrims crossing the border for the 550th birth anniversary of the founder of Sikhism Guru Nanak Dev.

"It allows Indian Sikh pilgrims to visit Gurdwara Kartarpur Sahib, an important Sikh house of worship just inside the Pakistan border. This impressive project will transform a remote three-acre site across a sensitive international boundary," Ortagus said.

"Congratulations to Pakistan on this initiative, and our best wishes to the pilgrims making the crossing for the 550th anniversary of Guru Nanak's birth," Ortagus said.

Guru Nanak Dev spent the last 18 years of his life at Kartarpur Sahib, which has now become the world's largest Sikh Gurdwara.