President Joe Biden and Ukrainian President Volodymyr Zelenskyy on Thursday signed a 10-year bilateral security agreement at an international summit that included a deal on a multibillion dollar loan designed to help Kyiv defend against Russia's invasion.

“We’re not backing down. In fact, we’re standing together against this illegal aggression,” Biden said at a joint news conference Thursday night with Zelenskyy.

Biden and his counterparts from the wealthiest democratic nations also reached a deal Thursday to give Ukraine a $50 billion loan this year backed by frozen Russian assets, signaling a determined commitment to beat back Russia’s invasion, U.S. officials said.

As Ukraine struggles to preserve its independence amid Russia’s assault, the money will go toward military aid, humanitarian support and reconstruction of the country, a Biden administration official said in a press briefing.

Biden said that taken together, the security agreement and loan deal bolster Ukraine and send an unmistakeable message to Russian President Vladimir Putin, who launched the invasion of Ukraine more than two years ago.