Donald Trump, according to sources in several US media, has asked Zelenskyj to investigate the corruption rumors of Joe Biden's son, Hunter Biden, who has served on the board of a Ukrainian gas company. Trump also accuses Joe Biden of putting pressure on the Ukrainian government to protect his son.

The investigation should have been a requirement for continued military support from the United States to Ukraine.

The reporting has prompted some Democrats to again talk about putting the president before state law. When Trump met reporters on Monday, he said he was not taking that talk seriously, and defended the conversation with Zelenskyj.

"It's very important to talk about corruption," Trump said.

Trump confirmed during a press conference on Sunday that the two presidents discussed corruption and that Trump then said he did not want people like Joe Biden and his son Hunter Biden to contribute to the corruption in Ukraine. According to Trump, however, the conversation largely consisted of congratulations to Zelenskyj, who was then newly elected president.

Ukrainian Foreign Minister Vadym Prystayko has denied that Zelenskyj would have felt pressured during the conversation and one of Zelenskyj's employees guarantees that all investigations in Ukraine will be conducted in a transparent manner.