President Biden met with NATO allies on Thursday in an emergency session about Russia’s brutal war against Ukraine as the conflict reached the one-month mark.

The 30-member alliance gathered at its Brussels headquarters to talk about plans to beef up NATO troop rotations in countries along the southern portion of its eastern flank — and contingency plans in case Russian aggression intensifies.

“We are determined to continue to impose costs on Russia to bring about the end of this brutal war,” NATO Secretary General Jens Stoltenberg said as the meeting began, paying tribute to “the great courage of the Ukrainian people and the Ukrainian armed forces fighting for their freedom and their rights.”

Biden plans to announce new sanctions for Russia and new humanitarian aid for Ukraine and the millions of refugees fleeing the fighting. Together with G-7 leaders, he will talk about new measures to deter sanctions evasion.