There will be a formal impeachment inquiry against US President Donald Trump, but that is a long way from saying he will be removed from office.

Political scientist Graham Dodds called the whistleblower complaint released Thursday morning "pretty damning."

"Trump released this thinking this would exonerate him and make him look good, and most people think it's done the opposite; it's made him look even worse," said Dodds.

The Whitehouse released the transcript of a conversation between Trump and Ukrainian President Volodymyr Zelensky Wednesday in which the president repeatedly asks Zelensky to work with Trump's lawyer and the US attorney general to investigate Democratic 2020 contender Joe Biden and his son.

In addition, Dodds said Trump's talk of withholding money in exchange for an investigation looks horrible.

"It doesn't look good. It's sleazy," said Dodds. "This is not the kind of way the US should be conducting business."

Impeachment, Dodds explained, is justified and is part of the American Constitution to investigate high crimes and misdemeanours against high-ranking officials, but it does not mean removal from office.

Two presidents, Andrew Johnson and Bill Clinton, have been impeached, but neither of them was removed.

The process is also very long, and the odds of it progressing by next year's election are not great.

Dodds added that it would be up to Republicans to remove Trump or challenge him for next year's nomination for the president.