WASHINGTON (AP) 鈥 Ukrainian President Volodymyr Zelenskyy is preparing to visit Washington on Wednesday, according to three AP sources, in his first known trip outside the country since Russia鈥檚 invasion began in February.

Two congressional sources and one person familiar with the matter confirmed plans for the visit. They spoke on the condition of anonymity because of the highly sensitive nature of the trip. They said Zelenskyy鈥檚 visit, while expected, could still be called off at the last minute due to security concerns.

The visit to Washington is set to include an address to Congress on Capitol Hill and a meeting with President Joe Biden. It comes as lawmakers are set to vote on a that includes about $45 billion in emergency assistance to Ukraine and as the U.S. prepares to send to the country to help stave off Russia鈥檚 invasion.

The visit comes a day after Zelenskyy made a daring and dangerous trip to what he called the hottest spot on the 1,300-kilometer (800-mile) front line, the city of Bakhmut in Ukraine鈥檚 contested Donetsk province, where he praised Ukrainian troops for their 鈥渃ourage, resilience and strength鈥 as artillery boomed in the background.

The Ukrainian leader told the troops he passed through Sloviansk, Kramatorsk and Druzhkivka to reach Bakhmut in an unannounced trip that appeared designed to show Moscow's failure to capture the city and dishearten trying to surround it.

鈥淏akhmut Fortress. Our people. Unconquered by the enemy. Who with their bravery prove that we will endure and will not give up what鈥檚 ours,鈥 he wrote on his Telegram channel, thanking the troops for "the courage, resilience and strength shown in repelling the enemy attacks.

"Since May, the occupiers have been trying to break our Bakhmut, but time goes by and Bakhmut is already breaking not only the Russian army, but also the Russian mercenaries who came to replace the wasted army of the occupiers,鈥 he said.

Russia鈥檚 invasion, which began Feb. 24, has lost momentum. The illegally annexed provinces of Donetsk, Kherson, Luhansk and Zaporizhzhia remain fiercely contested. Capturing Bakhmut would sever Ukraine鈥檚 supply lines and open a route for Russian forces to press on toward cities that are key Ukrainian strongholds in the Donetsk province.

In a video released by his office from the Bakhmut visit, Zelenskyy was handed a Ukrainian flag and alluded to delivering it to U.S. leaders.

鈥淭he guys handed over our beautiful Ukrainian flag with their signatures for us to pass on,鈥 Zelenskyy said in the video. 鈥淲e are not in an easy situation. The enemy is increasing its army. 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 鈥 it is not enough.鈥

The latest tranche of U.S. funding would be the biggest American infusion of assistance yet to Ukraine, above even Biden鈥檚 $37 billion emergency request, and ensure that funding flows to the war effort for months to come.

On Wednesday, the U.S. was also set to announce that it will send $1.8 billion in military aid to Ukraine in a major package that will for the first time include a Patriot missile battery and precision guided bombs for its fighter jets, U.S. officials said.

The aid signals an expansion by the U.S. in the kinds of advanced weaponry it will send to Ukraine to bolster its air defenses against what has been an increasing barrage of Russian missiles in recent weeks. The package will include about $1 billion in weapons from Pentagon stocks and $800 million in funding through the Ukraine Security Assistance Initiative, officials said.

The decision to send the Patriot battery comes despite threats from Russia鈥檚 Foreign Ministry that the delivery of the advanced surface-to-air missile system would be considered a provocative step and that the Patriot and any crews accompanying it would be a legitimate target for Moscow鈥檚 military.

It鈥檚 not clear exactly when the Patriot would arrive on the front lines in Ukraine, since U.S. troops will have to train Ukrainian forces on how to use the high-tech system. The training could take several weeks, and is expected to be done in Germany. To date, all training of Ukraine's forces by the U.S. and its Western allies has taken place in European countries.

Also included in the package will be an undisclosed number of Joint Direct Attack Munitions kits, or JDAMs. The kits will be used to modify massive bombs by adding tail fins and precision navigation systems so that rather than being simply dropped from a fighter jet onto a target, they can be released and guided to a target.

The visit comes at an important moment as the White House braces for greater resistance from a Republican-controlled House that鈥檚 signaled it will put more scrutiny on aid for Ukraine in the new Congress. GOP leader Kevin McCarthy has said his party鈥檚 lawmakers will not write a 鈥渂lank check鈥 for Ukraine.

Biden and Zelenskyy frequently have held phone calls in coordination with the White House announcing new tranches of military assistance for Ukraine. The calls have been mostly warm, with Biden praising Ukraine for remaining steadfast against the Russians and Zelenskyy thanking the U.S. president for support.

House Speaker Nancy Pelosi, who visited Zelenskyy earlier this year in Kyiv, encouraged lawmakers to be on hand for Wednesday evening鈥檚 session.

鈥淲e are ending a very special session of the 117th Congress with legislation that makes progress for the American people as well as support for our Democracy,鈥 Pelosi wrote Tuesday in a letter to colleagues. 鈥淧lease be present for a very special focus on Democracy Wednesday night.鈥

Later at the Capitol, Pelosi said of Ukrainians, 鈥淭hey are fighting for democracy for all of us."

For his part, Russian President Vladimir Putin on Tuesday hailed the 鈥渃ourage and self-denial鈥 of his forces in Ukraine 鈥 but he did so at a ceremony in an opulent and glittering hall at the Kremlin in Moscow, not on the battlefield.

Mercenaries from the Wagner Group, a shadowy Russian military contractor, are reported to be leading the charge in Bakhmut. Unverified videos on a popular Russian social media platform showed the Wagner Group's leader, Yevgeny Prigozhin, standing near an artillery piece and saying he was ready to meet Zelenskyy in Bakhmut.

At the Kremlin ceremony, Putin presented awards to the Moscow-appointed heads of the four illegally annexed regions of Ukraine.

鈥淥ur country has often faced challenges and defended its sovereignty,鈥 Putin said. 鈥淣ow Russia is again facing such a challenge. Soldiers, officers and volunteers are showing outstanding examples of courage and self-denial on the front line.鈥

In a video address honoring Russia's military and security agencies, he praised the security personnel deployed to the four regions, saying that 鈥減eople living there, Russian citizens, count on being protected by you.鈥

Putin acknowledged the challenges faced by the security personnel.

鈥淵es, it鈥檚 difficult for you,鈥 he said, adding that the situation in the regions is 鈥渆xtremely difficult.鈥

British authorities, meanwhile, gave a bleak assessment of how the war is going for Russia.

Some 100,000 Russian troops were 鈥渄ead, injured or have deserted鈥 in the invasion, U.K. Defense Secretary Ben Wallace said. Wallace didn鈥檛 give a figure for Ukrainian casualties, but the U.S. military recently put the estimated number of Ukrainian troops killed and wounded at about 100,000.

Losses in Russia's military command have also taken a toll, as has the destruction of equipment. 鈥淣ot one single operational commander then in place on Feb. 24 is in charge now,鈥 Wallace told lawmakers in the House of Commons. 鈥淩ussia has lost significant numbers of generals and commanding officers.鈥

鈥淩ussian capability has been severely hampered by the destruction of more than 4,500 armored and protected vehicles, as well as more than 140 helicopters and fixed wing aircraft,鈥 Wallace said.

Ukraine's counteroffensive has succeeded in recapturing large swaths of land. After 300 days of war, the U.K. Ministry of Defense tweeted, Ukraine has liberated about 54% of the maximum amount of extra territory Russia seized in the invasion. It didn鈥檛 say what portion of Ukrainian territory Russia controlled at the peak of its gains.

Russia now controls about 18% of internationally recognized areas of Ukraine, including those parts of the eastern Donbas and the Crimean Peninsula seized in 2014.

With the fighting in the east at a stalemate, Moscow has used missiles and drones to attack Ukraine鈥檚 power equipment, hoping to leave people without electricity as freezing weather sets in.

Life in the took a minor but welcomed step toward normality with the reopening of two of Kyiv鈥檚 main subway stations for the first time since the war began. The key hubs of Maidan Nezalezhnosti and Khreschatyk, like the capital鈥檚 other underground stations, have served as air raid shelters.

鈥淚t鈥檚 the feeling that despite everything, we are returning to a routine that we were used to,鈥 said 24-year-old passenger Denys Kapustin. 鈥淭his is very important.鈥

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Castillo reported from Kyiv, Ukraine. Lolita C. Baldor and Tara Copp in Washington and Andrew Katell in New York contributed.

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