Ukrainian President Volodymyr Zelenskiy, asked whether U.S. President Donald Trump had put improper pressure on him during a July phone call, said nobody can put pressure on him except his six-year-old son, Reuters reports.

Democrats in the U.S. House of Representatives on Tuesday launched a formal impeachment inquiry into Trump, accusing him of seeking Ukraine’s help to smear Democratic rival Joe Biden ahead of next year’s election. Trump has dismissed the inquiry as a witch hunt.

The allegations turn on a July 25 telephone call between Trump and Zelenskiy during which critics allege Trump improperly pressured his Ukrainian counterpart to investigate Biden, the former U.S. vice president, and his son Hunter, who had worked for a company drilling for gas in Ukraine.

Trump has said he did nothing wrong and that he’ll release a transcript of the conversation later on Wednesday to prove it.

Nobody can put pressure on me because I am the president of an independent state, Zelenskiy told Russian reporters in New York where he is attending the United Nations General Assembly.

The only one person by the way who can put pressure on me … is my son, who is six years old, said Zelenskiy whose comments were broadcast by the Rossiya 24 channel on Wednesday morning ahead of an planned meeting between Zelenskiy and Trump.

Asked whether he would ask Trump for anything when they met, Zelenskiy said:

Asking for something is not Ukraine’s style. It’s a new strong country and isn’t asking anyone for anything. We can help others ourselves.

Since the political scandal involving Trump and Ukraine erupted, a trip to the United States that began as a golden opportunity for Kiev to burnish relations with its most powerful international backer has turned into a diplomatic tightrope walk for Zelenskiy.