Russian missile strike near Poland raises tough questions for Biden

A Russian missile strike near Ukraine's border with Poland over the weekend raises tough questions for President Joe Biden and the U.S. response to the war in Ukraine.

President Joe Biden's dual promises to consider NATO's Article 5 a "sacred obligation" but also not to have U.S. forces engage with Russia in Ukraine may be increasingly difficult as Russian President Vladimir Putin expands the scope of his attack -- with a barrage of missiles striking near Ukraine's border with NATO ally Poland over the weekend, along with intense shelling in Kyiv overnight.

The U.S. has also warned about a possible chemical weapons attack and a senior administration official told ABC News earlier Monday that Russia is "desperately" asking for Chinese help -- with China "considering" giving the Russians "airstrike capabilities."

But amid signs that Putin is escalating, it remains unclear what consequences Russia would face from the U.S.

Russian forces targeted a military training site over the weekend in western Ukraine that had housed Western volunteers and members of the Florida National Guard training Ukrainian counterparts before the invasion. At least 35 people were killed and 134 injured, according to Ukrainian officials. There were "no Americans at all working there," Pentagon press secretary John Kirby said Sunday.