WASHINGTON: President Joe Biden warned his Kremlin counterpart Vladimir Putin in a phone call Saturday of “swift and severe costs” should Russia attack Ukraine, but the leaders´ call apparently produced no easing of tensions.In a statement, the White House said Biden stressed that “while the United States remains prepared to engage in diplomacy, in full coordination with our allies and partners, we are equally prepared for other scenarios.””President Biden was clear that, if Russia undertakes a further invasion of Ukraine, the United States together with our allies and partners will respond decisively and impose swift and severe costs on Russia,” the statement said.