Efforts to defuse the crisis in Ukraine via a frenzy of telephone diplomacy failed to ease tensions Saturday, with US President Joe Biden warning that Russia faces “swift and severe costs” if its troops carry out an invasion. Russian leader Vladimir Putin slammed Western claims that Moscow was planning such a move as “provocative speculation” that could lead to conflict in the ex-Soviet country, according to a Russian readout of a call with French President Emmanuel Macron. Speaking after new phone talks between Putin and Biden, the Kremlin’s top foreign policy advisor Yury Ushakov told a conf…