VATICAN CITY -- The Vatican's foreign minister, Archbishop Paul Gallagher, is heading to Kyiv this week as the Holy See seeks to balance its concern for Ukrainians amid Russia's war with its efforts to keep open a channel of dialogue with Moscow.

Gallagher is due to arrive May 18 and meet May 20 with Ukrainian Foreign Minister Dmytro Kuleba, a visit that was originally scheduled for before Easter but was postponed after Archbishop Gallagher came down with COVID-19.

The Vatican said that Archbishop Gallagher would stop first in Lviv to meet with refugees and regional officials, and then move onto Kyiv for the meeting with Kuleba and to tour the destruction nearby.

The secretariat of state tweeted May 17 that the visit would mark the 30th anniversary of diplomatic relations with Ukraine and show the closeness of the pope and Holy See to Ukraine, "reaffirming the importance of dialogue to reestablish peace."

The trip comes as the Holy See toes a delicate line in trying to keep alive newly improved ties with the Russian Orthodox Church while offering support to the "martyred" Ukrainian faithful. At the same time, the Holy See is reconciling Pope Francis' frequent denunciation of the weapons industry and "crazy" recourse to rearming Ukraine with Catholic teaching that says states have a right and duty to repel an "unjust aggressor."

"It has to be proportional," Archbishop Gallagher told RAI state television in announcing his trip. "Yes, Ukraine has the right to defend itself and it needs weapons to do it, but it has to be prudent in the way it's done."

Archbishop Gallagher, a 68-year-old career Vatican diplomat from Liverpool, becomes the third papal envoy dispatched to the region by Francis, after two trusted cardinals went to Ukraine and bordering countries to assess the humanitarian needs of Ukrainian refugees and bring them the pope's solidarity.

Pope Francis has drawn criticism from some for refusing to condemn Russia or President Vladimir Putin by name, though he has stepped up his criticism of the "barbaric" war and recently met with the wives of two Ukrainian soldiers holding out at the besieged steel mill in Mariupol, a gesture of "our concern and participation in the suffering of these families," Archbishop Gallagher said.

The pope's down-the-middle line is evidence of the Holy See's diplomatic tradition of not calling out aggressors by name and its efforts to keep open paths of dialogue with both sides in a conflict. This so-called "Ostpolitik" dictated the Vatican's Cold War policy of maintaining relations with the same Communist regimes that were persecuting the Catholic faithful on the ground.

In the case of Ukraine, the Holy See is keen not to sever newly improved relations with the Russian Orthodox Church, which took a big step forward in 2016 when Pope Francis met in Havana with the Russian Patriarch, Kirill.

The pope has so far declined an invitation from President Volodymyr Zelenskyy to visit Ukraine, recently saying he wants to go to Moscow first. Pope Francis has said he asked early on to meet with Russian President Vladimir Putin, but that the Russian leader hasn't yet replied.

Pope Francis, however, called off a planned June meeting with Kirill, who has justified Putin's war on ideological and spiritual grounds. The pope has said the Vatican's diplomats -- presumably Archbishop Gallagher and his boss, the secretary of state Cardinal Pietro Parolin -- realized the optics would be bad.