WASHINGTON, Dec 20 - President Volodymyr Zelensky is preparing to visit Washington on Wednesday, according to three AP sources, in his first known trip outside the country since Russia’s 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 Zelensky’s 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, The Associated Press reported. It comes as lawmakers are set to vote on a year-end spending package that includes about $45 billion in emergency assistance to Ukraine and as the U.S. prepares to send Patriot surface-to-air missiles to the country to help stave off Russia’s invasion.

The visit comes a day after Zelensky 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’s contested Donetsk province, where he praised Ukrainian troops for their “courage, resilience and strength” 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 the Russians trying to surround it.

“Bakhmut Fortress. Our people. Unconquered by the enemy. Who with their bravery prove that we will endure and will not give up what’s ours,” 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,” he said.

Russia’s 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’s 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, Zelensky was handed a Ukrainian flag and alluded to delivering it to U.S. leaders.

“The guys handed over our beautiful Ukrainian flag with their signatures for us to pass on,” Zelenskyy said in the video. “We 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 — it is not enough.”

The latest tranche of U.S. funding would be the biggest American infusion of assistance yet to Ukraine, above even Biden’s $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’s 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’s military.

It’s 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.

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

“We 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,” Pelosi wrote Tuesday in a letter to colleagues. “Please be present for a very special focus on Democracy Wednesday night.”

Later at the Capitol, Pelosi said of Ukrainians, “They are fighting for democracy for all of us.”

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

Some 100,000 Russian troops were “dead, injured or have deserted” in the invasion, U.K. Defense Secretary Ben 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’t say what portion of Ukrainian territory Russia controlled at the peak of its gains. (ap/ez)