By MATTHEW LEE and VLADIMIR ISACHENKOV
WASHINGTON (AP) — The failure of last week’s high-stakes diplomatic meetings to resolve escalating tensions over Ukraine has put Russia, the United States and its European allies in uncharted post-Cold War territory. It is posing significant challenges for the main players to avoid an outright and potentially disastrous confrontation. Unlike previous disagreements that have arisen since the collapse of the Soviet Union, the current Ukraine crisis carries real risks of debilitating economic warfare and military conflict that are exacerbated by the dangers of miscalculation and overreaction, particularly in Europe. The refusal thus far by each side to climb down from what the other regards as unrealistic and maximalist demands has left the prospects for diplomacy in limbo.