LONDON - Fighting has escalated around Ukraine's Russian-backed rebel regions, a development confirming the worst fears of Western governments: that an all-out Russian military strike against Ukraine is now almost inevitable, with Russia claiming as a justification the need to protect the rebels.

Yet the ultimate scope of such a Russian military operation remains a matter of debate, with the US administration believing that Russia would seek to occupy most of Ukraine, while some European governments still hope that Moscow's objectives may be more limited.