Pope Francis may visit Cuba this September as part of a trip that will also take him to the United States, the Vatican has announced, although discussions with Cuban authorities are at an early stage.

Vatican spokesman Federico Lombardi said "the Holy Father has taken into consideration the idea of carrying out a leg to Cuba on the occasion of his upcoming visit to the United States" between 22 and 27 September.

Fr Lombardi added contacts with Cuban authorities were "still at too early a stage to be able to talk about a firm decision and an operational plan".

The 78-year-old Catholic leader confirmed late in 2014 that he would visit the US to take part in a Catholic Church congress in Philadelphia.

During the trip, he will also address the United Nations in New York, become the first pontiff to address the US Congress and will meet with US President Barack Obama at the White House.

The popularity of the Argentine-born pope is soaring among Americans, according to recent polls.

A survey by the Pew Research Center released in March showed that 90% of Catholic Americans thought well of the pontiff, including 57% who held a "very favourable" view of him.

The Pontiff is also to tour Latin America in July, visiting Ecuador, Bolivia and Paraguay.

The Argentinian native visited Brazil in July 2013 but has not returned to Spanish-speaking Latin America since becoming pope.

The region is home to more than 425 million Catholics - nearly 40% of the world's Catholic population.