A top adviser to Vladimir Putin says that the Russian president threatened a full diplomatic break with the United States should Washington impose new sanctions on Russia.

Speaking to Russian state media following a conversation between Presidents Putin and Biden late Thursday evening Moscow time, Yuri Ushakov noted that Biden had again warned that the U.S. and its allies would impose new sanctions on Russia should it invade Ukraine. Such sanctions, the former ambassador to Washington said, would be a “colossal mistake” by the U.S. that would risk a “complete rupture of relations” between the two countries.