Speaking after a NATO summit that saw the alliance also agree to take in Finland and Sweden, Biden said the United States and its NATO allies were united in standing up to Russian President Vladimir Putin.
"I don't know how it's going to end, but it will not end with Russia defeating Ukraine," Biden told a news conference. "Ukraine has already dealt a severe blow to Russia."
Biden, who appeared to be readying allies for a long conflict in Ukraine despite talk in March of a possible victory, added: "We are going to support Ukraine for as long as it takes." He declined to give more details.
The pending formal announcement of more weapons would come on top of the more than $6.1 billion already announced by the United States since Russia forces rolled into Ukraine on Feb. 24 and brought full-scale war back to Europe.
"The U.S. is doing exactly what I said we would do if Russia invaded, enhance our force posture in Europe," Biden said. "The United States is rallying the world to stand with Ukraine."
The Madrid NATO Summit this week produced aid for Ukraine from other nations.
British Prime Minister Boris Johnson has joined Biden in pledging another 1 billion pounds ($1.22 billion) in military aid to Ukraine.
Britain's contribution includes air defense systems and new electronic warfare equipment, taking support to more than 2.3 billion pounds since Moscow's invasion, a financial sum the British government said was second only to U.S. aid.
The aid comes as Russian President Vladimyr Putin did not appear ready to withdraw or negotiate the terms of a peace deal, Johnson said.
"There doesn't seem to be anything to talk about. Because it's not only that the Ukrainian people would find it very difficult to do a deal, Putin isn't even offering a deal," Johnson told a news conference.
In Addition to the U.S. and British aid, President Emmanuel Macron said France would soon deliver six more CAESAR guns.
Putin said on Wednesday that Russia would respond in kind if NATO deployed troops or infrastructure in Finland or Sweden, who have decided to join NATO after years of neutrality.
Estonian Prime Minister Kaja Kallas said the West needed to be ready, particularly in terms of possible attacks on Finnish, Sweden and NATO computer networks. "Of course, we have to expect some kind of surprises from Putin, but I doubt that he is attacking Sweden or Finland directly," she said.