The United States is preparing to impose further sanctions on Russia over the poisoning of prominent opposition leader Aleksei Navalny, national security adviser Jake Sullivan said on Sunday. “We are preparing another package of sanctions to apply in this case,” Sullivan said during an appearance on CNN’s “State of the Union,” referring to the treatment of the imprisoned opposition leader. “We’ve shown all along the way that we are not going to pull our punches, whether it’s on Solar Winds, or election interference, or Navalny when it comes to responding to Russia’s harmful activities,” Sullivan told host Dana Bash. The United States “will take a backseat to no one,” said Sullivan when questioned on the timing of the additional sanctions. “It will come as soon as we have developed the packages to ensure that we are getting the right targets,” he added. “And when we do that, we will impose …