U.S. Talks Set Amid Russian Offensive
Drone strike set rail cars on fire in Kharkiv.
Train with 200+ passengers had 18 in hit carriage; 5 bodies found.
Zelenskyy called strike terrorism, urging allies to pressure Russia.
Next United States-brokered talks expected on February 1.
Ukraine's air force neutralized 135 of 165 attack drones.