A man at the centre of America's latest political storm kicked off the second day of speeches Wednesday at this year's gathering of world leaders.

Ukrainian President Volodymyr Zelenskiy's first-ever address at the United Nations came just a few hours after a formal U.S. House impeachment inquiry into U.S. President Donald Trump was launched -- a development that was sparked partly by a July 25 phone call between Trump and Zelenskiy.

In his speech, Zelenskiy steered clear of the American scandal and focused on the horrors of war and Ukraine's ongoing conflict with Russia.

At issue is whether Trump abused his presidential powers and sought help from Ukraine to undermine his Democratic foe, former Vice-President Joe Biden, and help his own re-election.

In the days before the phone call, Trump ordered advisers to freeze $400 million in military aid for Ukraine, prompting speculation that he was holding up the money as leverage for information on Biden.

Trump has denied that charge but acknowledged pressing Zelenskiy to investigate Biden and his son Hunter, who served on the board of a Ukrainian energy company.

Democrats, who control the House leadership, say they need to know whether Trump abused his office to seek a foreign government's help in trying to dig up dirt on an opponent. Trump has denied that the funds were blocked as leverage for information on the Bidens and says he did nothing wrong, calling the matter a "witch hunt."

In a TV interview over the weekend, Ukraine's foreign minister denied Zelenskiy was pressured to investigate Hunter Biden. Zelenskiy's office, however, has declined to comment on the reports.

The United States has been one of Ukraine's most steadfast allies, giving it millions of dollars in aid, since a pro-Western government took power in Kyiv in 2014. That same year, Russia annexed Ukraine's Crimean Peninsula and threw its weight behind separatists fighting in eastern Ukraine.

Zelenskiy, a popular 41-year-old comedian with no political experience, unseated incumbent Petro Poroshenko in an election this year in the nation of 45 million people. Zelenskiy campaigned on promises to fight corruption and engage Russia in order to end the conflict in eastern Ukraine. The fighting has killed more than 13,000 people and displaced 1 million.

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Vasilyeva reported from Moscow