Ukrainian President Volodymyr Zelensky said he is on his way to Washington, where he will meet US President Joe Biden on Wednesday.
This is his first foreign trip since the invasion of Russia in February.
The White House confirmed the flight, adding that Washington would supply Ukraine with Patriot missile batteries, significantly increasing the country’s air defense capability.
Zelensky will address Congress and hold a number of meetings.
“On my way to the United States to strengthen the flexibility and defense capabilities of Ukraine,” the Ukrainian president wrote on Twitter.
Zelensky regularly hosts foreign leaders in the capital, Kyiv, and has visited troops across Ukraine.
Ukraine’s president has spoken frequently to world leaders by phone and via videoconference – often from his office in Kyiv.
But the sudden visit to a foreign country is the first since the start of the war, and also indicates the importance of Ukraine’s relationship with the United States, which has played a leading role in providing military support.
The new Patriot missile system, promised by the United States, will enable Ukraine to protect its infrastructure from Russian attacks. Ukrainian officials have long demanded more powerful air defense systems from the West.
Russia targets the Ukrainian energy sector, where millions live in the dark in winter, and suffer from temperatures several degrees below zero.
The White House, in its briefing before Zelensky’s visit, also confirmed a new package of about $2 billion in security assistance to Ukraine.
Work is underway to advance a bill that would give Ukraine more than $40 billion in additional financing as it approaches 2023.
The United States is the country most committed to total spending on direct military support to Kiev since the beginning of the conflict.
President Zelensky demanded more money, saying that the monthly cost of defending Ukraine is about $5 billion.
His visit to Washington comes a day after he made an unannounced visit to the front-line city of Bakhmut, where Ukrainian and Russian forces have been fighting a fierce battle for months.
The presidency said he met the soldiers and handed out rewards to them.
The visit was an important display of defiance, and a show of support for Ukrainian forces engaged in some of the fiercest fighting in recent weeks.
The soldiers gave Zelensky the Ukrainian flag with their names signed on it, and asked him to hand it over to President Biden and the US Congress, at a moment captured by the cameras.
On the same day, Russian President Vladimir Putin awarded medals inside the Kremlin to personalities involved in the Russian invasion.
The US military estimates that at least 100,000 Russian and 100,000 Ukrainian soldiers have been killed or wounded since Russia invaded Ukraine on February 24, along with about 40,000 civilians.
The United Nations has registered 7.8 million people as refugees from Ukraine across Europe, including Russia. But the figure does not include those who were forced to flee their homes and remain in Ukraine.