President Moon said after the Mass that their prayers in St. Peter's will "resound as echoes of hope in the hearts of the people of the two Koreas as well as the people of the whole world who desire peace."
"Just as your holiness prayed before the U.S.-North Korea summit, we are paving a desirable way toward assuring a peaceful future for the Korean Peninsula and the world," Moon said.
The pope and the Korean president exchanged gifts, including a medallion of olive branches as a message of peace and a Korean image of the Virgin Mary.
When Pope Francis saw Moon's gift of a sculpture of the face of Jesus by a Korean artist, he remarked that he could see the suffering of the Korean people in Christ's crown of thorns.
Last month, Moon traveled to Pyongyang for the third inter-Korean summit with North Korean leader Kim Jong Un. The leaders of the two Koreas pledged to make a joint bid for the 2023 Summer Olympics.
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During their meeting, Kim Jong Un asked the South Korean leader to extended an invitation to Pope Francis for a papal visit to North Korea. Kim told Moon that he would "greatly welcome" the pope in Pyongyang, according to South Korea's presidential office.
A South Korean bishop attending the 2018 Synod of Bishops said last week that a papal visit to Pyongyang would be "a giant step forward for peace on the Korean peninsula," but cautioned that there must be "some sort of religious freedom" before such a visit takes place.
North Korea has consistently been ranked the worst country for persecution of Christians by Open Doors. Christians within the atheist state have faced arrest, re-education in labor camps, or, in some cases, execution for their faith.
A United Nations investigation in 2014 produced a 372-page report that documented crimes against humanity, including execution, enslavement, torture, imprisonment, forced abortions, and knowingly causing prolonged starvation.
The U.S. State Department estimates that there are currently an estimated 80,000 to 120,000 people in North Korea's six political prison camps.