Europe's leaders are scrambling. Their hastily convened security summit in Paris on Monday is proof of that.

They are still reeling from not being invited by the US to talks with Russia over the future of Ukraine. US President Donald Trump said on Sunday he could be meeting Russian President Vladimir Putin "very soon".

Can Europe, under pressure, put political differences and domestic economic concerns aside, and come up with a united front on security spending and on Ukraine's future, including potentially sending troops there - to force themselves a spot at the negotiating table?