Volodymyr Zelenskyy is set to travel to the United States to meet President Joe Biden at the White House.
The trip would mark the first time the Ukrainian president has left Ukraine since Russia invaded on 24 February.
The visit has not yet been confirmed by Washington amid concerns over Mr Zelenskyy’s security and could still be called off at the last minute.
Ukraine war latest: Belarus ‘likely deflected’ Putin’s efforts
The Ukrainian president is set to address Congress on Capitol Hill.
He will also meet congressional leadership and national security committee chiefs from the Republican and Democratic parties, according to Punchbowl News.
US House of Representatives Speaker Nancy Pelosi said there would be a session of Congress on Wednesday evening which would have a “very special focus on democracy”.
US politicians are set to vote on a year-end spending package, including around $45bn (£37bn) in emergency assistance to Ukraine. Meanwhile the US is preparing to send Patriot surface-to-air missiles to aid the country in repelling Russia’s invasion.
The funding would be the biggest American infusion of assistance yet to Ukraine, surpassing President Biden’s $37bn (£30bn) emergency request and will ensure funding flows to the war effort for months to come.
Mr Zelenskyy has addressed various parliaments and international organisations by video throughout Russia’s invasion and has sent his wife to foreign capitals to call for support.
A surprise visit to troops on the frontline
It comes after Mr Zelenskyy made a surprise visit to troops in the frontline city of Bakhmut in Ukraine’s contested Donetsk province.
Visiting the scene of some of the most intense combat since Russia invaded Ukraine, Mr Zelenskyy praised his troops’ “courage, resilience and strength”.
Please use Chrome browser for a more accessible video player
Zelenskyy says he believes Russia must be held accountable
In a video released by his office, Mr Zelenskyy was handed a Ukrainian flag and hinted at delivering it to US leaders.
“The guys handed over our beautiful Ukrainian flag with their signatures for us to pass on,” Mr Zelenskyy said.
“We are not in an easy situation. The enemy is increasing its army, and our people are braver and need more powerful weapons. We will pass it on from the boys to the Congress, to the president of the United States. We are grateful for their support, but it is not enough. It is a hint – it is not enough.”