Shortly before the inauguration of the Ukrainian president in May, a collaborator of Rudolph W. Giuliani went to Kiev to give a warning to the new leadership of the country, said a lawyer of the collaborator.

L & # 39; s partner, Lev Parnas, told a representative of the new government that he should announce an investigation into Trump's political rival, Joseph R. Biden Jr., and his son, or vice-president Mike Pence would not attend the swearing in of the new president, and the United States would freeze the help, said the lawyer.

The complaint of Mr Parnas, who is preparing to share his story with the impeachment investigators, challenges the story of the events reported by Mr Trump and Ukrainian officials at the heart of the congressional investigation. It also directly links Mr Giuliani, the president's personal attorney, to threats of repercussions against the Ukrainians, which he vigorously denied.

But Mr Parnas' story, though potentially important, is contradictory on many fronts. None of the people involved questioned the holding of the meeting, but Parnas said alone that his intention was to present an ultimatum to Ukrainian leaders.