WARSAW (Reuters) - U.S. Vice President Kamala Harris will head to Romania on Friday and discuss the growing refugee crisis in the region, a day after talks between Ukraine and Russia's foreign ministers failed to bring any pause in the conflict.

       Harris will meet President Klaus Iohannis in Bucharest, her second stop on a three-day trip through eastern Europe. Meanwhile, the United States, together with the Group of Seven nations and the European Union, will move to revoke Russia's "most favoured nation" status in an effort to pressure it to end the conflict with Ukraine.

       Harris met Polish leaders and Ukrainian refugees in Warsaw on Thursday and offered U.S. support to calls for an international war crimes investigation against Russia. Her visit to Poland came amid a rift between the United States and Poland over supplying warplanes to Ukraine.

       Polish President Andrzej Duda asked for more help to house and feed Ukrainians fleeing the conflict, and said he had asked Harris that Washington speed up the process for refugees who sought to go to the United States and might have family there.

       About 1.43 million Ukrainians have fled to Poland since the invasion began on Feb. 24. Over that same time, more than 291,081 Ukrainians have fled to Romania.

       In total, more than 2.3 million people have fled Ukraine as of March 10, according to the United Nations, which has warned that up to 5 million people could flee. That would make it the biggest humanitarian crisis in Europe since World War Two.

       The U.S. Senate on Thursday approved legislation to help Ukraine finance ammunition and other military supplies, as well as humanitarian support.

       Russia, which calls its actions in Ukraine a "special operation", to disarm its neighbour and dislodge leaders it calls neo-Nazis, has denied targeting civilians.

       (Reporting by Nandita Bose in Washington)