evidence: The US and Russia both indicated on Thursday that the ball is in the other’s court when it comes to deterring an invasion of Ukraine, showing little sign that a diplomatic agreement is imminent as Russian President Vladimir Putin has continued to mass forces near Ukraine’s border – despite a direct warning by President Joe Biden earlier this month to de-escalate. Speaking just hours after Putin’s marathon year-end news conference, in which he said Russia’s actions will depend on the US’s and NATO’s "unconditional ensuring of Russia’s security today and in the future," the US official said the Biden administration is prepared to discuss some of Russia’s concerns. [...] In his annual year-end news conference on Thursday, Putin deflected when asked whether Russia plans to invade Ukraine. "How would the Americans react if, on their frontier with Canada, we deployed our missiles?" he told reporters. "It’s a question of security, and you know our red lines."