US and Ukrainian flags are displayed outside the White House for the visit of Ukraine's President Volodymyr Zelensky, on his first trip outside his country since Russia invaded

Washington (AFP) - Days before the year-end holiday, downtown Washington’s streets were dominated Wednesday not just by Christmas decor but by the flag of Ukraine, marking the surprise visit to the US capital by Volodymyr Zelensky.

Pennsylvania Avenue, the grand boulevard which links the White House and Congress, was blocked off for the one-day visit of Ukraine’s president, while banners of Ukrainian yellow and blue were paired with the US flag’s red, white and blue.

Outside of the White House, Zelensky’s first stop of the day, television cameras from around the world were there to record the visit of the wartime leader, his only known trip outside his country since Russia invaded exactly 300 days ago.

Americans called him heroic and compared the visit to that of Britain’s premier Winston Churchill, who came to Washington in 1941 and addressed the Congress on wartime cooperation between the two allies – as Zelensky did later Wednesday evening.

Before he addressed the special joint session of Congress, Zelensky was greeted by President Joe Biden in the White House Oval Office, where they sat next to a crackling fireplace.

In the freezing weather outside, Ukraine supporters lined security barriers to show their support.

Ukraine's President Volodymyr Zelensky meets with US President Joe Biden in the White House Oval Office

Yarema, a 17-year-old Ukrainian student in the United States, was wrapped in the Ukrainian flag, hoping to see Zelensky as well as visit the city.

“I wanted to show my support to our president and my support to Ukraine,” he said.

Asked what Zelensky should be requesting from Biden, Yarema replied: “Arms, arms and even more arms.”

- Intense security -

A Ukraine supporter outside the White House during the visit of President Volodymyr Zelensky, while a US Secret Service official stands guard

Bakhtiar Mendybay, 35, who traveled nearly an hour with his children from his home in Virginia to the White House, said he could not miss the event.

He had one hand on a stroller and the other wielding a sign which showed Zelensky calling for more weapons.

“I’m here today to greet the greatest man alive,” said the native of Kazakhstan, which like Ukraine is a former part of the Soviet Union and still under significant Russian influence.

“Ukrainians, they’re fighting for everyone, including my country, my people. I mean, they stand up against Russian imperialism,” said Mendybay, who has lived in the United States for 10 years.

Security was tight, with hundreds of police and Secret Service officers out in force for Zelensky’s visit.

“We are very cognizant that Russia has assets in this country and might try to do something,” a senior official of the US Capitol Police told ABC television.

“We know what is at stake,” the official said.

- ‘Slava Ukraini’ -

House Speaker Nancy Pelosi gifts a US flag to Ukrainian President Volodymyr Zelensky after receiving a Ukrainian national flag from him following his address to Congress

At the other end of Pennsylvania Avenue past Washington’s City Hall which was illuminated in blue and yellow, lawmakers and top Biden administration officials gathered to listen to Zelensky’s address to Congress.

Multiple members of the audience wore blue suits or yellow accents in honor of the visit, while some male members pinned Ukrainian flags on their lapels.

Entering the House chamber, where members are expected to pass another massive Ukraine aid deal later this week, Zelensky was met with a thunderous standing ovation.

A handful of Republicans strongly aligned with former president Donald Trump, who have expressed concerns over the US support for Ukraine, notably refused to applaud.

Zelensky’s speech, delivered in English, stretched for more than 20 minutes, including more standing ovations and occasional bursts of laughter, such as when the Ukrainian president – a former comedian – ventured a pun on Vladimir Putin’s name.

After exchanging a Ukrainian flag from the frontlines of the war with a US flag that had flown Wednesday over the US Capitol, Zelensky departed under another round of applause.

A group of Ukrainians in the visitors area chanted “Slava Ukraini” (“Hail to Ukraine”), with several American lawmakers on the chamber floor joining in.