Pope Francis has left Rome for a nine-day pastoral visit to Cuba and the United States Saturday – his longest trip yet as pontiff.

During his travels the Argentinian pope is expected to meet Cuban President Raul Castro as well as Fidel Castro, call for an end to the U.S. embargo on Havana as well as make an appeal for better treatment for dissidents by Cuba’s communist rulers.

The special papal jetliner left Leonardo da Vinci Airport at 10.35 a.m. [0835 GMT] and was due to arrive in Havana at 4 p.m. local time. President Castro was due to meet the 78-year-old pontiff at the Jose Marti International Airport where both men were to make speeches.

On Sunday, Pope Francis' official program starts with a Mass to be celebrated in the vast Plaza de la Revolucion.

The visit to Cuba is the climax of Francis' major personal triumph in engineering a rapprochement and restoration of diplomatic relations between Washington and Cuba, a role that Raul Castro and U.S. President Barack Obama praised in a telephone conversation recently, the White House disclosed.

On Tuesday, Francis will travel to the United States where he will meet President Obama and address both Congress and the United Nations.

The pontiff will stop at Philadelphia to celebrate a major Mass during which his homily, like all his utterances during the trip, will be closely watched for signs of changes in policy on the role of women in the Church and subjects such as priestly celibacy, homosexuality, birth control and the ban on divorced Catholics taking communion at Mass.

The Vatican's white-and-yellow flag will for the first time be hoisted over the UN headquarters in New York, Sept. 25 – the morning after the pontiff arrives in the city.

This follows a decision by the UN general assembly last week to allow countries with observer status such as the Vatican and Palestine to fly their flags at the UN.