(NewsNation) —  President Joe Biden is set to meet with NATO and European Union leaders in Brussels next week in response to Russia’s attacks on Ukraine, the Associated Press is reporting.

Three sources told Reuters that the plan, which is still being finalized, could change given the rapidly evolving situation in Ukraine.

It’s been 20 days since Russian President Vladimir Putin started his attacks on Ukraine, causing a humanitarian crisis to which the world is struggling to find a solution. Russian troops continued to bombard Ukraine’s largest cities Tuesday, with large explosions thundering across its capital of Kyiv shortly before dawn. Nine humanitarian corridors have been opened for evacuees.

Russia has stepped up its assault on Ukraine in recent days, with artillery strikes on Irpin and the northwest Kyiv suburbs of Hostomel and Bucha.

Rare glimmers of hope amid the chaos have been spotted. A convoy of 160 civilian cars left Mariupol along a designated humanitarian route, the city council reported

Mariupol, a 430,000-resident strategic port city, has been under a two-week siege, with no electricity, gas, or water. Reports detail corpses lying in the street, people melting snow for drinking water and hungry people fighting over food as Russian troops continue the assault.

Leaders from Poland,  the Czech Republic and Slovenia announced they would travel to Kyiv Tuesday to show support for besieged Ukraine.

A total of 596 civilian deaths recorded since Feb. 24 have been reported by the United Nations, though the organization believes the true toll is much higher.