<p>Moscow: Russian Deputy Foreign Minister Sergei Ryabkov said on Tuesday that the involvement of the United States in Ukraine's ongoing incursion into Russia's western Kursk region is "a fact", the <em>TASS</em> state news agency reported.</p><p>Ryabkov did not offer evidence to back up that assertion, but he said, without offering details, that Moscow's response may be much tougher than before, another state news agency, <em>RIA</em>, reported.</p><p>The White House has said it had no prior knowledge of the Ukrainian operation.</p>
<p>Moscow: Russian Deputy Foreign Minister Sergei Ryabkov said on Tuesday that the involvement of the United States in Ukraine's ongoing incursion into Russia's western Kursk region is "a fact", the <em>TASS</em> state news agency reported.</p><p>Ryabkov did not offer evidence to back up that assertion, but he said, without offering details, that Moscow's response may be much tougher than before, another state news agency, <em>RIA</em>, reported.</p><p>The White House has said it had no prior knowledge of the Ukrainian operation.</p>