MOSCOW — The U.S. ambassador to the United Nations vowed that the U.N. Security Council will press Russia hard in a Monday session to discuss Moscow's massing of troops near Ukraine and rising fears it is planning an invasion."Our voices are unified in calling for the Russians to explain themselves," Ambassador Linda Thomas-Greenfield said of the U.S. and the other council members on ABC's "This Week" program on Sunday. "We're going into the room prepared to listen to them, but we're not going to be distracted by their propaganda." Russia's assembling of an estimated 100,000 troops near the border with Ukraine has brought increasingly strong warnings from the West that Moscow intends to invade. Russia in turn demands that NATO promise never to allow Ukraine to join the alliance, and to stop the deployment of NATO weapons near Russian borders and roll back its forces from Eastern Europe.The head of Russia's Security Council, Nikolai Patrushev, on Sunday rejected Western warnings about an invasion."At this time, they're saying that Russia threatens Ukraine — that's completely ridiculous," he was quoted as saying by state news agency Tass. "We don't want war and we don't need it at all."The United States and European Union countries say a Russian invasion would trigger heavy sanctions. On Sunday, the chairman of the U.S. Senate's Foreign Relations Committee raised the prospect of imposing some punishments preemptively."There are some sanctions that really could take place up front, because of what Russia's already done — cyberattacks on Ukraine, false-flag operations, the efforts to undermine the Ukrainian government internally," Sen. Bob Menendez said on CNN.In the event of an invasion, Menendez said, Russia would face "the mother of all sanctions," including actions against Russian banks that could severely undermine the Russian economy and increased lethal aid to Ukraine's military. The sanctions would apparently be significantly stronger than those imposed after Russia annexed Crimea from Ukraine in 2014. Those penalties have been seen as ineffective.Russia has long resented NATO's granting of membership to countries that were once part of the Soviet Union or were in its sphere of influence as members of the Warsaw Pact. NATO "has already come close to Ukraine. They also want to drag this country there," Russian Foreign Minister Sergey Lavrov said on Sunday, "although everyone understands that Ukraine is not ready and could make no contribution to strengthening NATO security."Ukraine has sought NATO membership for years, but any prospects of joining appear far off as the country struggles to find political stability and attack corruption.U.S. Sen. Dick Durbin, a member of the Senate's Ukraine Caucus, suggested that Ukraine's backing off its NATO aspirations could expedite a diplomatic solution to the current crisis.If Ukrainian President Volodymyr Zelenskyy "decides that the future membership, if there's to be one in NATO for Ukraine, and the question of the Russian occupation of Ukraine are two things to put on the table, I think we may move toward a solution to this," Durbin said on NBC.Ukraine has not shown signs of willingness to make concessions on potential alliance membership.Lavrov also underlined Russia's contention that NATO expansion is a threat, saying the alliance has engaged in offensive actions outside its member countries."It is difficult to call it defensive. Do not forget that they bombed Yugoslavia for almost three months, invaded Libya, violating the U.N. Security Council resolution, and how they behaved in Afghanistan," he said.The U.S. and NATO have formally rejected Russia's demands about halting NATO expansion, though Washington outlined areas where discussions are possible, offering hope there could be a way to avoid war.Russian President Vladimir Putin has made no public remarks about the Western response. Lavrov has said West's position leaves little chance for reaching agreement, though he also said Russia doesn't want war. Copyright 2022 NPR. To see more, visit https://www.npr.org.