. >> i'm scott pelley. those stories, tonight, on "60 minutes." ( ticking ) >> stahl: the threat of a russian invasion of ukraine keeps escalating, as last-minute diplomacy continues. president vladimir putin says ukraine belongs with russia, and wants a promise it will never join nato, the western military alliance. but his saber-rattling has produced exactly what he was trying to prevent: more nato and u.s. troops in eastern europe. still, yesterday, ukrainian president volodymyr zelensky angrily called on the west to do more, saying this is not about war in ukraine, this is about war in europe. today president biden met with the national security council at the white house, and secretary of state blinken repeated the u.s. view that putin's plan to invade "is moving forward." we spoke late in the week with the foreign minister of ukraine, dmytro kuleba, about the crisis, at the front. >> dmytro kuleba: we still see a room for diplomacy to-- let's put it this way-- demotivate president putin from resorting

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. >> i'm scott pelley. those stories tonight on "60 minutes." but first, holly williams with the latest from ukraine this evening. >> williams: today, russian ground forces continued to press ukraine's two largest cities, kharkiv, and the capital, kyiv. it's the fourth day of war here, but as the sun set, ukraine's government and the kremlin agreed to hold talks. yet, in an unnerving sign of how things could escalate, president vladimir putin ordered russia's nuclear forces on higher alert, while the u.s. and europe have increased their weapons shipments to ukraine. ( explosion ) resistance here has looked determined, with videos emerging of killed and captured russian soldiers, and destroyed russian tanks and vehicles. ukrainian volunteers have taken up arms, and others have prepared molotov cocktails at the request of their government. ( explosion ) moscow claims it hasn't targeted civilians, but ukraine says russian forces have fired indiscriminately. look at this. we've seen people here taking cover in the subway, where many are sleeping at