Ukrainian President Volodymyr Zelensky is reportedly poised to visit the White House and the US Capitol later on Wednesday, in his first visit since the Russian invasion of his country.

There were multiple reports in the US media on Wednesday (AEDT) that Mr Zelensky was on his way to the Washington, although no official confirmation.

The visit was under a shroud of secrecy because of security concerns. One source said the media leaks about a potential visit were “not helping.”

However, one senator, Delaware’s Chris Coons, confirmed the plans to US publication The Hill. He said Mr Zelensky’s visit was a “terrific opportunity” as the US Congress was about to pass another major package of support for Ukraine.

Mr Zelensky is expected to address a joint session of Congress, as well as meeting congressional leadership and national-security committee chiefs from the Republican and Democratic parties.

House Speaker Nancy Pelosi has written to US politicians warning them of a session of Congress on Wednesday night with a “very special focus on democracy”. She has refused to confirm it is for a visit by Mr Zelensky’.

“A complete and total hero in the Congress of the United States fighting for democracy, leading people who are fighting for democracy, would bring honour to the Congress of the United States,” she said.

“[But] I don’t know that that’s going to happen. We don’t know yet. We just don’t know.”

Mr Zelensky is also expected to have a sit-down meeting with US President Joe Biden, at which another $US1.8 billion ($2.7 billion) in security assistance will be announced for Ukraine.

CNN reported on Wednesday that the new announcement would add add to the nearly $US20 billion ($30 billion) in US security assistance provided to Ukraine since Russia’s invasion began last February.

The White House has refused to comment on Mr Zelensky’s visit or confirm any announcement by Mr Biden.

Wednesday’s speculation came just hours after the Ukraine president made a surprise trip to troops in the battered eastern frontline city of Bakhmut. In a Tuesday night video address, he referred to his trip to “Fortress Bakhmut” in Donetsk, one of the provinces Russia claimed in September but most countries reject as illegal occupation.

Mr Zelensky last left Ukraine for the Munich Security Conference on February 19, according to his official schedule. His spokesman did not immediately respond to a written message seeking confirmation.

The President has addressed many international parliaments by video since the Russian invasion of Ukraine, including the US Congress and Australia’s House of Representatives.

Mr Zelensky’s wife, Olena Zelenska, met Mr Biden and wife Jill Biden at the White House in July.

-with AAP