United States President Joe Biden is looking to boost unity and ramp up sanctions on Moscow at a day-long string of summits in Brussels as the West responds to the Kremlin's bid to upend the post-Cold War balance.

"Vladimir Putin has already crossed the red line into barbarism," said British Prime Minister Boris Johnson as NATO leaders arrived for a meeting and the war marked one month.

"The harder our sanctions, the tougher our economic vice around the Putin regime, the more we can do to help the Ukrainians, I think the faster that this thing can be over," he said.

Estonian Prime Minister Kaja Kallas called on the 30-nation alliance to "double our efforts" to check the Kremlin's aggression against its pro-Western neighbor.

"Putin cannot win this war," she said. "We have to stop the war criminal."

Ukrainian President Volodymyr Zelensky, whose country is not in NATO, was set to appeal for more advanced weaponry and greater intervention in a video address to leaders as he seeks to cajole the West into a tougher response. 

Popular

Why EV makers choose Vietnam, not nickel-rich Indonesia

Jakarta library reopens to packed rooms, long queues

State-sanctioned intolerance