G7 leaders gather Thursday for the first day of an Italy summit, hoping to seal a deal on providing $50 billion for Ukraine using frozen Russian assets.

Ukrainian President Volodymyr Zelensky will join US President Joe Biden and leaders from Italy, Britain, France, Germany, Canada and Japan at the luxury Borgo Egnazia resort in Puglia.

The G7 leaders hope to agree on an urgent $50 billion loan to help Kyiv with defence, budgetary support and help for reconstruction after more than two years of war with Russia.

The loan would be secured against the future profits from interest on 300 billion euros ($325 billion) of Russian central bank assets frozen by Western allies.

"We are on the verge of a good outcome here," US National Security Advisor Jake Sullivan said.

"Hopefully by the time that leaders meet today, we will have a common vision on the way forward," he told reporters ahead of the formal opening of the summit.

But he said delegations were still thrashing out the details, including how many countries would "step up" and the kind of financial vehicle involved.

"We have the major tentpoles of this decided but some of the specifics will be left to be worked through by experts on a defined timetable," he told reporters.

French President Emmanuel Macron's office on Wednesday said a deal had been agreed on providing $50 billion for Ukraine before the end of the year, but said that technical details still needed to be finalised.

The European Union agreed earlier this year to use the profits from the frozen Russian assets for Ukraine, worth up to three billion euros a year.

But the idea at the G7 is to use this to provide more and faster help through a massive upfront loan.

Zelensky is attending the Puglia summit as part of a week of diplomatic efforts to rally support, which will culminate in an international conference on Ukraine in Switzerland this weekend.

G7 nations are also expected to announce further bilateral support, with Biden and Zelensky due to sign a US-Ukraine security deal, and Britain announcing up to $310 million for Kyiv.

The US this week announced a raft of new sanctions aimed at constraining Moscow's war machine, while raising the stakes for foreign banks that still deal with Russia. 

Mideast, China

The summit comes at a time of extraordinary global turmoil.

As well as the conflict in Ukraine, the Hamas-Israel conflict is raging and economic tensions are rising between China and Western countries.

Many G7 countries are also in political flux. Everyone in Puglia is aware this could be Biden's last G7 summit if he loses to Donald Trump in November US elections.

Britain's Rishi Sunak is tipped to be ousted in July 4 elections, while France's Macron and Germany's Olaf Scholz are both under pressure after gains by the far right in EU elections last weekend.

The G7 summit opens Thursday morning with a short session on Africa, development and climate change, before turning to the Middle East.

The leaders have already announced their support for a Gaza truce deal outlined by Biden, which would also see the release of hostages taken in Hamas's October 7 attack on Israel.

Jordan's King Abdullah II -- a strong supporter of the Palestinian cause whose country signed a peace treaty with Israel 30 years ago -- is among around a dozen non-G7 guests also attending who are not, however, participating in the working sessions.

They include Turkish President Recep Tayyip Erdogan, UAE president Sheikh Mohamed bin Zayed and India's Narendra Modi.

Brazilian President Luiz Inacio Lula da Silva -- whose country holds the rotating G20 presidency this year -- as well as Argentina's Javier Milei and UN Secretary General Antonio Guterres also plan to attend.

All the guests are invited to a dinner Friday night at the Borgo Egnazia luxury hotel complex, built in the style of a traditional village.

With security extremely tight, the venue is far away from protesters and journalists, with the media centre located some 60 kilometres away in Bari.

Another key issue in Puglia, to be discussed Friday, will be concerns about China's so-called "industrial overcapacity", particularly in green energy and technology sectors such as solar panels and electric vehicles.

China said Thursday it "reserves the right" to file a suit with the World Trade Organization over planned new EU tariffs on imports of its electric vehicles.

The US, EU and Japan have all voiced concern that generous subsidies from Beijing are resulting in a flood of cheap goods hitting the global market, threatening Western firms.