Presidents Joe Biden and Volodymyr Zelensky signed a landmark 10-year security deal between Washington and Kyiv on Thursday in what the Ukrainian leader called a historic day in the fight against Russia's invasion.
The deal will see the United States provide Ukraine with a range of military aid and training over the next decade, while Zelensky said it would act as a bridge to his country finally winning prized membership of the NATO alliance.
Signed shortly after a G7 summit agreed on a separate deal to loan Ukraine $50 billion based on frozen Russian funds, it comes as the White House tries to lock in support for Kyiv with an election battle with Donald Trump looming.
"Today is a truly historic day," Zelensky said at a joint press conference with Biden after they signed the security agreement at a luxury resort near the G7 summit site in southern Italy.
Biden said they had taken "major steps at the G7 that collectively show (Russian President Vladimir) Putin he cannot wait us out."
The agreement says that the United States and Ukraine must consult within 24 hours "at the highest levels" after any future armed attack by Russia.
It also pledges to build up Ukraine's military, cooperate on training and work to build up Ukraine's domestic arms industry.
"Our security agreement is a bridge to Ukraine's membership in NATO," Zelensky told the press conference.
The United States has previously said Ukraine should have a path to membership but says that is impossible while it is still at war with Russia, as under NATO's mutual defence treaty its Western allies would have to go to war with Russia.
Biden meanwhile defended his decision to let Ukraine use US arms for short-range cross border attacks in the Kharkiv region, where Russia is mounting an offensive, but said longer-range attacks were still barred.
Zelensky meanwhile called for more Patriot air defence missiles to protect Ukraine against Russia's campaign of missile attacks.
Biden said five countries had already pledged to give Patriots to Ukraine, and said they would have to wait for the United States to replenish them until Ukraine's needs were fully met.
Zelensky also said that Chinese leader Xi Jinping had promised not to send Russia weapons to use against Ukraine -- though Biden said Beijing was already contributing to Moscow's war effort by giving economic and industrial support.
The US-Ukraine deal is similar to one that the United States has with its close Middle Eastern ally Israel. Washington has supplied Israel with arms as it fights Hamas in Gaza following the October 7 attacks.
While the Ukraine accord aims to commit future administrations to also support Ukraine, Trump could in theory end the agreement if he wins a second term in November.
But US officials insisted it would still build lasting support for Ukraine.
"Today, the United States is sending a powerful signal of our strong support for Ukraine now and into the future," said a US statement accompanying the security agreement.
Japan signed a similar security pact with Ukraine at the G7 summit.
Kyiv has now signed at least 15 similar deals in the past year with its major Western backers outlining multi-year commitments to fund and enhance Ukraine's defence and military.
Separately in Italy, the Group of Seven rich nations reached a US-backed deal for a new $50-billion loan for Ukraine using profits from frozen Russian assets.
Both the US-Ukraine accord and the assets deal reflect a push by the Biden administration to lock in support for Kyiv.
Republican former president Trump, who is neck-and-neck in the polls with Democrat Biden, has previously been cool on support for Ukraine and said he could force through a peace deal in 24 hours.
With Trump having previously praised Russian President Vladimir Putin and other autocrats, many in Kyiv fear that he would pressure them to accept Russia keeping hold of a chunk of Ukraine.
"The security-related commitments in this agreement are intended to support Ukraine's efforts to win today's war and deter future Russian military aggression," the US-Ukraine agreement said.
