FILE PHOTO: a meeting of RRussian Foreign Ministry spokeswoman Maria Zakharova attends a news conference in Moscow, Russia, March 13, 2018. REUTERS/Sergei Karpukhin/File Photo

MOSCOW (Reuters) - Russian Foreign Ministry spokeswoman Maria Zakharova said on Thursday that Moscow was starting to work on retaliatory measures after the United States announced a new round of sanctions against Moscow.

Washington said on Wednesday it was imposing fresh sanctions on Russia by the end of August after determining that Moscow had used a nerve agent against a former Russian agent and his daughter in Britain, something the Kremlin denies.

Zakharova told reporters at a briefing that no evidence had been presented to prove Russia’s blame, and that the pretext for the new round of sanctions had been made up.