Polish Prime Minister Mateusz Morawiecki has warned that Europe will receive of an influx of "millions" of migrants if border policies remain lax.
Speaking in an interview with German tabloid Bild, he said that he did not rule out the danger of war in view of developments on the Polish-Belarusian border.
"If we are not able to keep out thousands of immigrants now, soon there will be hundreds of thousands, millions, coming towards Europe," Morawiecki told Bild.
"If we don't decisively protect and defend our borders in Europe, hundreds of millions from Africa or the Middle East will try to come to Europe and especially to Germany," he said.
Morawiecki described the situation at the Belarusian border, where thousands of migrants are trying to reach the EU country of Poland, as stable with a growing risk.
Around 900 migrants on the border with Poland have spent the night from Wednesday to Thursday outdoors for the 11th consecutive day despite the low temperatures. They tried to warm themselves at campfire sites.
Many of them complained of breathing difficulties due to the smoke from the fires.
Due to the threaten of rain, the Belarusian authorities want to prepare more emergency shelters. Not far from the border, the storage facilities of a logistics company was opened on Monday as a sleeping camp.
"Belarusian forces are provoking more and more directly. I hope they don't take that one step too far in the process," Morawiecki said. "Because we Poles are determined to protect our border by all means. The eastern border of Europe and also of NATO."
Meanwhile, humanitarian aid for the stranded migrants in Belarus is being expanded. A field kitchen has been set up at the sleeping camp to provide people hot meals and drinks. Until now, migrants were sometimes left empty-handed after food distribution.
According to the Polish Ministry of Defence, a group of around one hundred migrants tried to break through the border barrier near the village of Dubicze Cerkiewne on Wednesday night, but without success.
Morawiecki said he was pleased to have the support of Germany and other NATO states. Now a joint declaration by Poland, Lithuania and Latvia could follow.
"Another step could be to activate Article 4 of the NATO Treaty, which officially states the violation of their territories," he said. The article provides for consultations between the allies, but not yet for military assistance.
Morawiecki added that it was not known what Belarus and Russia were planning.
"It is also possible that the crisis on the border is only meant to distract from new military attacks that (Russian President Vladimir) Putin is preparing in Ukraine," he said.