After meeting with European leaders on Thursday, President Joe Biden addressed questions at a NATO headquarters news conference in Brussels. He spoke out about warnings of a possible Russian attack on Ukraine with chemical weapons.

Biden had warned that Russia could use chemical weapons against Ukraine. His first question was whether the U.S. had gathered intelligence to suggest that Russian President Vladimir Putin might be considering using them. If so, he asked if the U.S. and NATO would respond militarily.

“I’m not going to give you intelligence data, number one,” Biden said. “Number two, we would respond. We would respond if he uses it, and the nature of the response would depend on the nature of the use.”

ABC News Chief White House Correspondent Cecilia Vega followed up, and asked, “If chemical weapons were used in Ukraine could that trigger a military response from NATO?”

“It would trigger a response in kind,” Biden replied. “Whether or not — you’re asking whether NATO would cross — we’d make that decision at the time.”

Biden didn’t explain what this response would look like, nor did he say whether it would include sending troops to Ukraine. This is something Biden has promised not to do.

Biden began by announcing a series of new sanctions against Russia that target the majority of Russian elites and the Duma. He also announced that the U.S. would welcome 100,000 refugees from Ukraine, and will provide $1 billion in humanitarian aid. This comes as Biden faces pressure from Zelenskyy, who wants to deliver more goods to Ukraine.

“Putin is getting exactly the opposite of what he intended to have as a consequence of going into Ukraine,” Biden said, adding later on that he was “banking on NATO being split.”

Biden is scheduled to travel to Poland on Friday.