CHICAGO—Treasury Secretary Janet Yellen said on Wednesday that the United States and Western allies have immobilized half of the assets of the Russian central bank and will continue to impose “severe consequences” on Russian President Vladimir Putin and the wealthy oligarchs who support him if he escalates his war in Ukraine. Yellen, speaking in Chicago to promote President Joe Biden’s economic agenda, said the Treasury has “made it a priority to go after oligarchs or Russian elites who are key to President Putin’s corrupt power”. “We have sanctioned many of these individuals over the last few weeks and we are assembling a task force with Justice Department colleagues and our allies to uncover, freeze, and seize their wealth around the world.” Yellen, who visited Chicago’s Ukrainian Village neighborhood with Illinois Governor Jay Pritzker, said that the United States and allies around the world have worked together to isolate Russia, making it more much more difficult for Putin to finance Russian aggression against Ukraine. …