Roger Stone, longtime political ally of U.S. President Donald Trump, arrives for his arraignment at U.S. District Court in Washington, U.S., January 29, 2019. REUTERS/Leah Millis

WASHINGTON (Reuters) - President Donald Trump’s longtime political ally Roger Stone on Tuesday will enter a not guilty plea in federal court, where he faces seven criminal counts as part of U.S. Special Counsel Robert Mueller’s Russia investigation, his lawyer told a U.S. judge.

U.S. prosecutors have charged Stone with making false statements to Congress, obstruction of an official proceeding and witness tampering.