The United States pledged long-term support for Ukraine in its war with Russia Thursday under a 10-year security deal being signed by President Joe Biden and his Ukrainian counterpart Volodymyr Zelensky.

The accord, being signed at the G7 summit in southern Italy, comes as the White House tries to lock in support for Kyiv as a tense US presidential election battle with Donald Trump looms.

"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 shortly before the signing.

The agreement would see United States provide Ukraine with a range of military aid and training as it battles Russia's invasion, with Washington vowing to protect its ally "now and into the future."

But while the 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.

Biden and Zelensky were holding a joint press conference and signing ceremony at a luxury resort in the Puglia following talks with G7 leaders in Puglia focused on boosting support for Ukraine.

The deal, which is similar to one the United States has with Israel, commits Washington to train the Ukrainian military, provide defence equipment, carry out combined exercises and work together on defence industry cooperation.

But unlike membership of the NATO alliance it does not commit the United States to send forces to defend Ukraine.

Similar deals

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.

On Wednesday, US National Security Advisor Jake Sullivan said the agreement aimed to transcend America's deep political divisions and provide consistent aid for Kyiv.

Those divisions played out recently when pro-Trump Republicans in the US Congress blocked Biden's request for billions of dollars in military aid for Ukraine for six months, before finally relenting.

Russia used the resulting halt in US support to launch a major offensive in Ukraine's northeastern Kharkiv region. Washington says that push has now stalled as new weapons filter through to Kyiv.

"If Vladimir Putin thinks that he can outlast the coalition supporting Ukraine, he's wrong. He just cannot wait us out, and this agreement will show our resolve and continued commitment," Sullivan said.