On Friday night, Mr. Giuliani rejected that characterization, asserting in a brief interview, “My only purpose was to make sure the investigation continued.”
The change of plans came as advisers were urging the incoming Ukrainian president, Volodymyr Zelensky, a comedian and political newcomer, not to meet with Mr. Giuliani, according to a person familiar with the conversations.
Mr. Giuliani had requested the meeting with Mr. Zelensky through intermediaries, but it had not been confirmed.
Mr. Giuliani’s foray into Ukrainian politics comes at a delicate moment for the country, which is deeply reliant on the United States for financial and military aid. The current Ukrainian government has sought to distance itself from matters related to the special counsel’s investigation of Russia’s interference in the 2016 presidential race.
Mr. Zelensky is set to take office on June 3.
The investigations had been opened by Ukrainian prosecutors during the term of the country’s current president, Petro O. Poroshenko. He lost his re-election bid last month to Mr. Zelensky, who has said that he would like to replace the country’s top prosecutor, who oversaw some of the matters.
Mr. Giuliani and other Trump allies had been working behind the scenes with the prosecutor to gather information about the investigations.
Mr. Giuliani said he feared he would have been “walking into a trap” had the meeting with Mr. Zelensky occurred. He predicted that it would have been misrepresented by advisers of Mr. Zelensky who have criticized the top prosecutor, singling out a member of Ukraine’s Parliament, Serhiy A. Leshchenko, who has advised the incoming president.