high-stakes trip president biden is making to brussels later this week, where he will participate in a nato summit. yesterday, it was announced his trip now will also include a stop in warsaw, where he will meet with the polish president. earlier, biden spoke with european allies, his counterparts in france, germany, italy and the uk to discuss their coordinated responses to russia's aggressions. today, u.s. summoned u.s. ambassador to russia saying biden's comments last week calling putin a war criminal and a pure thug, those were unacceptable and that ties between the two countries are, quote, on the verge of breaking. joining us now is nbc news correspondent cal perry live from lviv, ukraine. cal, tell us more about what you're seeing and hearing on the ground, especially when it comes to ukrainian citizens who are at the forefront of this terrible, bloody, costly invasion. >> reporter: yeah, so i think, alex, what we saw over the