A top American diplomat has urged Pope Francis to take a hard line with Russian President Vladimir Putin in regards to the ongoing Russia-Ukraine conflict when the two meet Wednesday, according to the Guardian. Francis, who has often said he opposes war, has not joined the West in condemning Russia’s actions in Ukraine since the country annexed Crimea in March 2014, sparking continued unrest in the region.

“Maybe this is an opportunity for the Holy Father to privately raise those concerns,” Kenneth Hackett, the U.S. ambassador to the Holy See, told reporters. He added that the Vatican could “say more about concerns on territorial integrity.”

Hackett also addressed the Kremlin’s apparent involvement in the Ukraine conflict. "It does seem that Russia is supporting the insurgents,” he said. “And it does seem that there are Russian troops inside Ukraine. This is a very serious situation."

Wednesday’s expected sidebar between Putin and Francis, their second meeting since they first met in November 2013, would take place in Milan, where Putin is visiting Russia’s pavilion at the 2015 Expo World’s Fair. The two had previously discussed the Ukraine situation during their 2013 meeting, but that was before the annexation of Crimea and the fighting between pro-Russia separatists and Ukraine. The topic is reportedly open for discussion Wednesday.

"Traditionally, a wide range of topical issues is addressed at meeting with the Pope,” the Kremlin’s spokesman Dmitry Peskov told reporters this week. “Obviously, it is a perfect possibility to exchange views on the most pressing problems.”

Francis has previously lamented the loss of life in Ukraine and encouraged both sides to respect the ceasefire, however he has stopped short of criticizing Russia’s actions. His silence on the issue has been viewed as a way for the pontiff to maintain relations with the Orthodox Church of Russia, according to the Associated Press.

The pope has previously said he opposes military action to solve conflict. “War always marks the failure of peace. It is always a defeat for humanity,” Francis said in 2013 from the Vatican.