Pope Francis will visit Indonesia, Papua New Guinea, East Timor, and Singapore in September, the Vatican announced Friday, an ambitious trip that could test the 87-year-old's increasingly fragile health.

Running from September 2 to 13 and covering around 30,000 kilometers (18,600 miles) in total, the trip is the longest for the Argentine since he became head of the worldwide Catholic Church in 2013.

"He will visit Jakarta from 3 to 6 September, Port Moresby and Vanimo from 6 to 9 September, Dili from 9 to 11 September, and Singapore from 11 to 13 September," the Vatican said in a statement.

The visit, his first abroad since September last year, has been on the cards for months, but the pontiff's health issues had raised questions on whether it would go ahead.

Francis pulled out of a key Easter event at the last minute in March and has asked aides to read several of his speeches in recent weeks due to a bout of bronchitis.

The pontiff, who uses a wheelchair, has suffered increasing health problems in recent years, from knee pain to surgery for a hernia and on his colon.

He is known for his work ethic -- he never takes holidays -- but has been forced to make concessions to his age and health, including canceling a trip to UN climate talks in Dubai last year.

Francis had been due to visit Papua New Guinea, East Timor, and Indonesia in September 2020 but the trip was canceled because of the coronavirus pandemic.

  Tolerance, unity, and peace 

 Involving more than 30 hours of flight, an eight-hour time difference, and a series of meetings and masses, the September trip will represent a major physical challenge.

But the pontiff loves being among his flock, and his arrival is keenly awaited.

The government in Indonesia, home to the world's largest Muslim population, had already announced the pope's visit last month, describing it as a "special gift" for the country's Catholics.

In a statement Friday, its foreign ministry said the visit was important "for all religious communities".

"The visit is also expected to strengthen the message of tolerance, unity, and world peace," it said.

According to the Pew Research Centre, Indonesia is home to 242 million Muslims and around 29 million Christians -- 8.5 million of whom are Catholics.

Authorities in Papua New Guinea had also announced in January his visit, but no trips are considered official until the Vatican confirms.

Papua New Guinea is home to more than nine million Christians -- almost the entire population -- though most Papua New Guineans are Protestant while retaining many traditional animist beliefs.

A 400-year-old version of the King James Bible, bound in calfskin, sits in the center of the country's parliament.

The last papal visit was in 1995 when Pope John Paul II was met with tribal dancers adorned with the feathers of exotic birds, grass skirts, and loincloths.

Since becoming pope 11 years ago, Francis has made 44 trips abroad, the most recent to Marseille, France, in September.

He has also announced plans to visit Belgium this year, while he has mentioned a possible visit home to Argentina.

Francis also has three coming trips planned within Italy, the first of which will be to Venice on April 28.