Hangar, one can argue that the UK already took a side (as did the US) a couple of decades ago by underwriting the deal wherein Ukraine gave up the nukes as part of the split from Russia/CIS/USSR.
Remind me again who has been targetting civilians in this ?
As for the agreement, US Govt has said previously it didn't apply when they disliked parts of it.................... funny that been saying that since 1860's in the US.