WASHINGTON (AP) — Prospects for meaningful diplomacy between the United States and Russia on any number of fronts are grim with the two countries locked in their worst confrontation since the Soviet-era Cuban missile crisis. Both sides have kept lines of communication open since Russia’s invasion of Ukraine. But those channels, opened at the height of the Cold War to reduce nuclear miscalculation and tension, have gone largely unused as Russia has intensified its war in Ukraine. And an ongoing but unrelated diplomatic spat has significantly reduced staffing at the countries’ embassies in Moscow and Washington.