A top White House advisor has warned that the United States is preparing another round of sanctions against Russia over the alleged poisoning of Kremlin critic Alexei Navalny.

President Joe Biden's National Security advisor Jake Sullivan told American media that "We sanctioned Russia for the poisoning of Alexei Navalny... We rallied European allies in a joint effort to impose costs on Russia for the use of a chemical agent against one of their citizens on Russian soil”.

 Sullivan added "We are preparing another package of sanctions to apply in this case, as well. We've shown along the way we're not going to pull our punches”.

Russia has rejected as baseless the accusation that it was behind the Navalny poisoning. Moscow says it will respond logically to any new sanctions. It also says the sanctions over the Navalny affair are linked to its energy distribution via the Nord Stream 2 pipeline that will serve some European countries including Euro heavyweight Germany. In January, Moscow arrested and jailed the opposition leader when he returned to Russia after recovering from the alleged poisoning.

In March, Washington imposed sanctions on a series of government officials and entities including the director of Russia's FSB security agency over the case.

Diplomatic relations between Moscow and Washington had all but broken down since Biden took office in January. Biden likened Putin to a "killer" and in March Russia took a rare step by recalling its ambassador to Washington. The U.S. administration acted likewise. A recent summit between Biden and Putin sought to ease tensions. Following the bilateral meeting, the Russian and American ambassadors returned to their posts, however, it appears that ties have dipped again.