Officials at the Pentagon have provided a clearer picture of the situation on the ground in Ukraine. They say Russian forces are closing in on the capital, Kyiv, from three directions.

The officials say the closest unit reached Antonov Airport, 20 kilometers from the center of the city. Another force is pushing in from Chernihiv, to the northeast. A third is moving from Sumy, about 60 kilometers away.

Russian pilots have been unable to take control of the airspace. That has prompted ground commanders to rely on long-range artillery and missile strikes.

The Russians have repeatedly targeted civilians. Still, their negotiators offered to set up "humanitarian corridors" to allow safe passage to the residents of five cities. They proposed routes leading to Russia and to Belarus, but Ukrainian negotiators rejected the offer.

Since the invasion began on February 24, more than 2 million people have fled.