YAOUNDE - Pope Leo sets off on Saturday for Angola, where he is expected to address exploitation of natural resources in the oil-rich country on the third leg of his four-nation Africa tour, during which he has taken on a new forceful speaking style.

Leo, who has been attacked repeatedly by President Donald Trump this week after the pope criticized the Iran war, will arrive from Cameroon, where on Thursday he said the world was "being ravaged by a handful of tyrants".

The first U.S. pope was due to arrive in Luanda, Angola's capital, around 3 p.m. (1400 GMT).

Before leaving Cameroon, Leo celebrated a farewell Mass in the capital, Yaounde, urging participants not to lose hope despite the challenges faced by the Central African country, which include a simmering conflict in its two anglophone regions that has killed thousands.

"In moments when we seem to be sinking, overcome by adverse forces, when everything appears bleak ... Jesus is with us always, stronger than any power of evil," said the pontiff.

"In every storm, he comes to us and repeats: 'I am here with you: do not be afraid'," said Leo.

ANGOLA FACES POVERTY DESPITE OIL WEALTH

In Angola later on Saturday, the pope was due to meet President João Lourenço before addressing the country's political leaders.

After decades of bloody conflict in the 20th century, Angola became one of the leading oil-producing nations in sub-Saharan Africa, with the sector accounting for some 95% of its exports.

Its population of 36.6 million people is still confronting extreme poverty, with more than 30% living on less than $2.15 per day, according to the World Bank.

More than half of the country identifies as Catholic.

Leo, originally from Chicago, kept a relatively low profile for a pope in his first 10 months, but in recent weeks has become outspoken on a range of issues. He has issued sharp denunciations of war and inequality on the ambitious, 10-day Africa tour.

Crowds greeting the pope on his visit to Cameroon were enthusiastic, including an estimated 120,000 people who attended a Mass on Friday in Douala, lining the streets along his routes and wearing colorful fabrics featuring images of his face.

-Joshua McElwee; Editing by Robbie Corey-Boulet and Alex Richardson/Reuters