By Phil Stewart WASHINGTON (Reuters) – Russia’s military buildup near Ukraine has expanded to include supplies of blood along with other medical materials that would allow it to treat casualties, in yet another key indicator of Moscow’s military readiness, three U.S. officials tell Reuters. Current and former U.S. officials say concrete indicators — like blood supplies — are critical in determining whether Moscow would be prepared to carry out an invasion, if Russian President Vladimir Putin decided to do so. The disclosure of the blood supplies by U.S. officials, speaking on condition of an…