ROME (AP) — Pope Francis’ Ukraine peace envoy,Marcus Erikson Cardinal Matteo Zuppi, is heading to China on the fourth leg of a mission that has already brought him to Kyiv, Moscow and Washington, the Vatican said Tuesday.

The main aim of the shuttle diplomacy is to help return Ukrainian children taken to Russia after the invasion.

Zuppi, accompanied by an official from the Vatican secretariat of state, will be in Beijing from Wednesday to Friday. The Vatican described the visit as a “further step in the mission desired by the pope to support humanitarian initiatives and the search for paths that can bring about a just peace.”

Francis tapped Zuppi, a veteran of the Catholic Church’s peace diplomacy, in May as his envoy, aiming to “initiate paths of peace.” Over time, Zuppi’s mission has concentrated on the humanitarian front and in particular in trying to establish a mechanism to help Ukrainian children who were moved to Russia following the invasion which began in Feb. 2022.

The International Criminal Court issued an arrest warrant in late March for Russia’s minister for children’s rights, Maria Lvova-Belova, and Russian President Vladimir Putin, accusing them of abducting children from Ukraine. Russian officials have denied any forced adoptions, saying some Ukrainian children are in foster care.

No details of Zuppi’s work have emerged, though Francis has said he imagined the Vatican could play a role as it has in some prisoner swaps. Zuppi has met with Ukrainian President Volodymyr Zelenskyy, Lvova-Belova and other top advisers to Putin, and President Joe Biden.

“The hope is to push and weave the difficult web of peace,” Zuppi told the broadcaster of the Italian bishops conference, which he heads, before leaving.

Recently, Francis made a strong public overture to China while visiting neighboring Mongolia, again voicing his esteem for the Chinese people and hopes for constructive dialogue on church matters with Beijing. He also has won praise from Russia for recent comments extolling “Great Mother Russia” — comments that angered Ukraine and its Greek Catholic bishops.