Poland's President Andrzej Duda again called on the United States to deploy nuclear weapons to Poland as a deterrent to Russia, the latest indication that the frontline NATO nation is increasingly considering nuclear protection as fears of Russia grow.

As President Trump casts doubt on U.S. alliances, Poland needs to double its military manpower and consider more destructive weapons, Prime Minister Donald Tusk said.

"The borders of NATO moved east in 1999, so 26 years later there should also be a shift of the NATO infrastructure east. For me, this is obvious," Polish President Andrzej Duda said.

Andrzej Duda believes Donald Trump could relocate U.S. nuclear warheads from Western Europe or the U.S. to Poland. He recently discussed the possibility with U.S. Special Envoy for Ukraine Keith Kellogg.