"It seems that the risk of war in the OSCE area is now greater than ever before in the last 30 years."
At a security meeting of 57 nations in Vienna on Thursday, Poland's foreign minister said Europe was closer to war than any time in the last three decades, as Russia said diplomatic efforts to defuse tensions over Ukraine... were hitting a dead end.
After the meeting, the U.S. ambassador to the Organization for Security and Cooperation in Europe said the West should prepare for a possible escalation in tensions with Moscow, adding: "The drumbeat of war is sounding loud."
Meanwhile, Russian snipers took part in military exercises near the Ukrainian border on Thursday, following tank drills the day prior.
Russia denies planning to invade Ukraine but says it needs guarantees from the West for its own security, including barring Ukraine from joining NATO and rolling back decades of alliance expansion in Europe - demands the U.S. has called "non-starters."
In an interview on Russian television, the country's deputy foreign minister said diplomacy must be given a chance but that Russian military specialists were providing options to President Vladimir Putin in case the situation worsened.
"We can no longer retreat. We can already see that there will be other measures, other actions against our opponents if they don't take into account our demands and our needs in the end."
Later on Thursday, U.S. National Security Adviser Jake Sullivan said at a White House press briefing that the U.S. was ready to respond to any Russian aggression.
"The United States and our allies and partners are prepared for any contingency, any eventuality. We're prepared to keep moving forward, down the diplomatic path in good faith and we're prepared to respond if Russia acts. And beyond that, all we can do is get ready and we are ready."
Russia has said it will decide on its next moves after this week's talks, but the pessimism from Russian officials cast grave doubt on the chances of a diplomatic breakthrough at one of the most fraught moments in East-West relations since the Cold War.