The United States and Russia are squaring off at U.N. Security Council over Ukraine, with Washington calling Moscow’s actions a threat to international peace and security, while a Kremlin envoy ridiculed Monday’s meeting as a “PR stunt.” The session kicks off more high-level diplomacy this week, although talks between U.S. and Russia have so far failed to ease tensions in crisis. Russia has massed an estimated 100,000 troops near Ukraine’s borders, stoking fears in West of an invasion. Russia denies it intends to launch an attack but demanded that NATO promise never to allow Ukraine to join alliance, halt deployment of NATO weapons near Russian borders, and roll back its forces from Eastern Europe. NATO and U.S. call those demands impossible. Russian Foreign Minister Sergey Lavrov and U.S. Secretary of State Antony Blinken didn’t make any visible progress in easing tensions at their meeting in Geneva earlier this month. They are expected to speak by phone Tuesday, according to Russian Foreign Ministry. U.S. President Joe Biden warned Ukrainian President Volodymyr Zelenskyy in a phone call Thursday that there is a “distinct possibility” Russia could begin an incursion in February, but Ukrainian leader sought to play down war fears, saying Western alarm over an imminent invasion has prompted many investors in country’s financial markets to cash out. Zelenskyy said Friday that “we aren’t seeing any escalation bigger than before,” and charged that Russian buildup could be an attempt by Moscow to exert “psychological pressure” and sow panic.