The U.S. would accept 100,000 Ukraine refugees under a proposal the Biden administration is expected to unveil Thursday.

A U.S. official, speaking on condition of anonymity, revealed the plan as President Joe Biden and European leaders marked one month since the start of Russia’s invasion of Ukraine with crucial summits in Brussels, Belgium.

In a video address to a NATO summit Thursday, Ukraine President Volodymyr Zelenskyy said Ukraine needs unlimited military assistance. Zelenskyy urged NATO to provide Ukraine with “1% of all your planes, 1% of all your tanks.”

“When we will have all this, it will give us, just like you, 100% security,” he said.

NATO Secretary General Jens Stoltenberg called the gathering to order, saying Russia will continue to face consequences if Moscow does not end its war.

“We are determined to continue to impose costs on Russia to bring about the end of this brutal war,” Stoltenberg said in opening remarks of the emergency NATO summit. “We pay tribute to the great courage of the Ukrainian people and the Ukrainian armed forces fighting for their freedom and their rights.

Stoltenberg also praised “those in Russia who are bravely speaking out against the war. We hear their voices, they matter.”

Biden will address the NATO summit before meeting with the leaders of the other G-7 countries and speaking to all 27 leaders of European Union countries. Biden is scheduled to cap the day with a news conference.

The U.S. and its allies are expected to announce new sanctions on Russia, additional humanitarian assistance for Ukrainians, and to call on China to condemn the invasion. They’ll discuss how to respond to a cyber, nuclear or chemical attack by Russia and what level of force presence is needed in Eastern Europe in the near and longer term.