A whistleblower complaint about President Trump threatens to overshadow his visit to the United Nations General Assembly this week.

President Trump arrived in New York Sunday night ahead of the United Nations General Assembly.

But before leaving the White House Sunday, the president seemed to confirm that he did discuss former Vice President Joe Biden and his son, Hunter, during a phone call with Ukraine's president in July.

"The conversation I had was largely congratulatory,... was largely the fact that we don't want our people, like Vice President Biden and his son, creating to the corruption already in Ukraine" said President Trump. 

The conversation is reportedly the basis of a whistleblower complaint against President Trump.

According to the Wall Street Journal, the president pressured the Ukrainian President eight times to investigate Hunter Biden, who worked for a Ukrainian gas company.

Over the weekend, Ukrainian's foreign minister denied suggestions his nation's leader was pressured. Now, Biden and other Democrats want the White House to release the transcript of the phone call.

President Trump says he's thinking of releasing it, but so far the White House has blocked congress' ability to see the complaint.