The scrutiny of Andriy Yermak, President Volodymyr Zelensky's chief of staff, could disrupt U.S.-led peace talks and further rattle Ukrainian politics.
The American pope emphasized a message of peace as he arrived in Ankara, welcomed on the tarmac by a military guard of honor and at the presidential palace by President Recep Tayyip Erdogan.
Russian President Vladimir Putin said the outlines of a draft peace plan agreed by the U.S. and Ukraine could become the basis of a deal to end the war.
