White House: Ultimately, Russia is responsible for tragic incident in Poland

US has full confidence in the Polish government's investigation of an explosion near their border with Ukraine a US spokesperson said.

Key quotes

• US sees nothing that contradicts Polish president's preliminary assessment explosion was most likely the result of a Ukrainian air defense missile.
• US spokesperson says whatever final conclusions may be, it is clear Russia is ultimately responsible 
• Ukraine has every right to defend itself.

More to come ...