(CNN)

U.S. Rep. Mike Quigley, D-Chicago, is co-chair of the Congressional Ukraine Caucus and was appointed to the escort committee for Ukrainian President Volodymyr Zelenskyy’s joint address to Congress.

Ukrainian President Volodymyr Zelenskyy speaks as he meets with President Joe Biden in the Oval Office of the White House, Wednesday, Dec. 21, 2022, in Washington. (AP Photo / Patrick Semansky)

In a brief remarks before reporters, President Joe Biden told Zelenskyy that “it’s an honor to be by your side” and he pledged continued financial, military and humanitarian aid for Ukraine. Biden also warned that Russia is “trying to use winter as a weapon” in the war.

People collect water from a Dnipro river in Kherson, Ukraine, Tuesday, Nov. 15, 2022. (AP Photo / Efrem Lukatsky)

Russia pounded Ukraine’s energy facilities Tuesday with its biggest barrage of missiles yet, striking targets across the country and causing widespread blackouts. A senior U.S. intelligence official said missiles crossed into NATO member Poland and killed two people.

An elderly man walks past a car shop that was destroyed after a Russian attack in Zaporizhzhia, Ukraine, Tuesday, Oct. 11, 2022. (AP Photo / Leo Correa)

Air raid warnings sounded throughout the country for a second straight morning as Ukrainian officials advised residents to conserve energy and stock up on water. Strikes in the capital and 12 other regions Monday caused power outages and pierced the relative calm that had returned to Kyiv and many other cities far from the war’s front lines.

Ukrainian President Volodymyr Zelenskyy, center, reacts after his press conference in Kyiv, Ukraine, Friday, Sept. 9, 2022. (AP Photo / Efrem Lukatsky)

The news came after days of apparent advances by Ukraine south of Kharkiv, the country’s second-largest city, in what could become the biggest battlefield success for Ukrainian forces since they thwarted a Russian attempt to seize the capital of Kyiv.

A man rides his bike past flames and smoke rising from a fire following a Russian attack in Kharkiv, Ukraine, March 25, 2022. (AP Photo / Felipe Dana, File)

Six months later, the largest military conflict in Europe since World War II has turned into a grinding war of attrition. The Russian offensive has largely bogged down as Ukrainian forces increasingly target key facilities far behind the front lines, including in Russia-occupied Crimea.

President Joe Biden walks to board Air Force One, Thursday, April 21, 2022, at Andrews Air Force Base, Md., en route to Portland, Ore. (AP Photo / Gemunu Amarasinghe)

The new package includes $800 million in military aid for much-needed heavy artillery, 144,000 rounds of ammunition and drones for the escalating battle in the Donbas region of eastern Ukraine. It builds on roughly $2.6 billion in military assistance that Biden previously approved.

Firefighters work to extinguish a fire after an airstrike hit a tire shop in Lviv, Ukraine, Monday, April 18, 2022. (AP Photo / Mykola Tys)

Russia bombarded the western city of Lviv and numerous other targets across Ukraine on Monday in what appeared to be an intensified bid to grind down the country’s defenses while building up its own forces for a major ground offensive in the east.

Ukrainian President Volodymyr Zelenskyy speaks via remote feed during a meeting of the UN Security Council, Tuesday, April 5, 2022, at United Nations headquarters. (AP Photo / John Minchillo)

Zelenskyy, appearing via video from Ukraine, told council members that civilians had been shot in the back of the head after being tortured, blown up with grenades in their apartments and crushed to death by tanks while in cars.

President Joe Biden speaks to the media at Fort Lesley J. McNair, Monday, April 4, 2022, as he returns to Washington and the White House after spending the weekend in Wilmington, Del. (AP Photo/Andrew Harnik)

President Joe Biden’s comments to reporters came after Ukraine President Volodymyr Zelenskyy visited Bucha, one of the towns surrounding Kyiv where Ukrainian officials say the bodies of civilians have been found. Zelenskyy called the Russian actions “genocide” and called for the West to apply tougher sanctions against Russia.

Halyna Falko looks at the destruction caused after a Russian attack inside her house near Brovary, on the outskirts of Kyiv, Ukraine, Monday, March 28, 2022. (AP Photo / Rodrigo Abd)

While hinting at possible concessions, President Zelenskyy also stressed that Ukraine’s priority is ensuring its sovereignty and its “territorial integrity” — preventing Russia from carving up the country, something Ukraine and the West say could now be Moscow’s goal.

A serviceman carries the photo of Capt. Andrei Paliy, a deputy commander of Russia's Black Sea Fleet, during a farewell ceremony in Sevastopol, Crimea, Wednesday, March 23, 2022. Paliy was killed in action during fighting with Ukrainian forces in the Sea of Azov port of Mariupol. (AP Photo)

A senior NATO military official said the alliance’s estimate was based on information from Ukrainian authorities, what Russia has released — intentionally or not — and intelligence gathered from open sources. The official spoke on condition of anonymity under ground rules set by NATO.

Displaced Ukrainians on a Poland-bound train bid farewell in Lviv, western Ukraine, Tuesday, March 22, 2022. (AP Photo / Bernat Armangue)

Civilians fleeing Mariupol said the city was under relentless bombardment, with block after block of destroyed buildings and corpses in the streets. But the Kremlin’s ground offensive in other parts of the country advanced slowly or not at all, knocked back by lethal Ukrainian hit-and-run attacks.

A man walks in his apartment ruined after the Russian shelling in Kyiv, Ukraine, Monday, March 21, 2022. At least eight people were killed in the attack. (AP Photo / Efrem Lukatsky)

As Russia intensified its effort to pound Mariupol into submission, its ground offensive in other parts of Ukraine has become bogged down. Western officials and analysts say the conflict is turning into a grinding war of attrition, with Russia bombarding cities.

Ukrainian President Volodymyr Zelenskyy speaks to the U.S. Congress by video to plead for support as his country is besieged by Russian forces, at the Capitol in Washington, Wednesday, March 16, 2022. (AP Photo / J. Scott Applewhite, Pool)

Livestreamed into the Capitol complex, Ukrainian President Volodymyr Zelenskyy said the U.S. must sanction Russian lawmakers and block imports. But rather than an enforced no-fly zone that the White House has resisted, he instead sought other military aid to stop Russian assault.

People clear debris outside a medical center damaged after parts of a Russian missile, shot down by Ukrainian air defense, landed on a nearby apartment block, according to authorities, in Kyiv, Ukraine, Thursday, March 17, 2022. (AP Photo / Vadim Ghirda)

Hundreds of civilians had been taking shelter in the grand, columned theater in central Mariupol after their homes were destroyed in three weeks of fighting in the southern port city.