"There was breaking news today, the Ukrainian president came out and said very strongly that President Trump did absolutely nothing wrong", Trump said. "That should be case over".
The US House Intelligence Committee is expected to release an impeachment report later on 2 December.
Earlier in the day, Zelensky denied there was a quid pro quo with Trump over US security assistance.
House of Representatives Intelligence Committee Chairman Adam Schiff has said the impeachment inquiry will go forward regardless of any pending litigation. Lawmakers have said they hope to conclude the inquiry before the New Year.
If the appeal is unsuccessful, the White House has the option of appealing to the US Supreme Court. Appeals will most likely delay the case well into 2020, if not longer.