WASHINGTON – President Joe Biden and Russian President Vladimir Putin spoke by phone on Thursday as tensions rise over a significant military buildup on the Ukrainian border. White House press secretary Jen Psaki said Biden urged Putin to de-escalate tensions with Ukraine and that his administration was prepared to "respond decisively" alongside allies and partners if Russia further invades Ukraine. During a prior call earlier this month, Biden did not accept Putin's "red line" and instead warned that Washington and European allies were prepared to impose a web of economic and political countermeasures if Ukraine's sovereign borders were breached.