As Prime Minister Rishi Sunak joins fellow leaders of the world’s major economies in Indonesia, here are answers to some key questions about the G20 summit.

– What is the G20?

The Group of 20 is an informal collection of many of the world’s biggest economic powers.

The leaders first met in response to the 2008 financial crisis, establishing the G20 as the main global forum for economic co-operation.

Finding consensus on international issues is not easy among the grouping as it encompasses geopolitical rivals such as the United States and China.

There have been disagreements over issues such as trade and climate, with divisions deepened by Russia’s invasion of Ukraine.

The group is made up of 19 countries and the European Union. The nations are Argentina, Australia, Brazil, Canada, China, France, Germany, India, Indonesia, Italy, Japan, Mexico, Russia, Saudi Arabia, South Africa, South Korea, Turkey, the UK and the US.

– What is the format of this year’s leaders’ summit?

Indonesia currently holds the G20 presidency and is hosting this year’s summit on the tropical island of Bali.

The two-day event, kicking off on Tuesday, is set to feature three plenaries: on food and energy security, health, and digital transformation.

The first, on food and energy, will effectively be a catch-all session, with Mr Sunak and allies set to use their speeches to confront Russia’s representative – expected to be Foreign Minister Sergei Lavrov – over Moscow’s invasion of Ukraine.

Ukrainian President Volodymyr Zelensky has been invited to address the event virtually.

There is plenty of time for Mr Sunak to have bilateral meetings and informal chats with other leaders at the margins of the summit.

The family photo in which leaders usually pose together at the annual gathering in a display of unity has been scrapped by the Indonesian hosts due to tensions over the Ukraine war.

Diplomats are also doubtful leaders will be able to agree a communique at the end of the summit, with none issued at previous finance or foreign affairs meetings this year.

– What will be discussed?

Although the gathering is structured around Indonesia’s priorities – energy and food, health and digital – it will inevitably be dominated by the fallout from the Ukraine war.

The world faces some of the most significant global economic challenges since the G20 was established, caused and exacerbated by Russia’s actions in Ukraine.

It is the first time G20 leaders are meeting since Russia launched its full-scale invasion in February.

As well as confronting Mr Lavrov, Mr Sunak will use the talks to call for co-ordinated action to address the difficulties.

His plan to strengthen the global economy includes ending Moscow’s “weaponisation” of food production and distribution, reducing energy dependence on Russia and helping developing nations grow without relying on “exploitative” lenders.

– What does Russia’s presence mean?

Russia’s membership of the G20 makes for a difficult dynamic at the summit.

Vladimir Putin was long expected to attend but is now sending Mr Lavrov in his place.

The Russian president’s decision to shun the event is seen by British officials as a sign of weakness because he is unwilling to face confrontation, as his military offensive suffers continued setbacks.

Mr Sunak is expected to rebuke Mr Lavrov with allies over the invasion and then avoid further interaction.

Russia’s top diplomat is prone to walk out when challenged over Ukraine, doing so at a G20 foreign ministers’ meeting in July.

Russia’s presence also means any joint statement will not condemn Moscow as it would never agree to condemn itself.

– What are Mr Sunak’s priorities at the summit?

As well as using the talks to confront Russia and influence the international agenda with his five-point economic action plan, Mr Sunak will want to use his first major international summit to establish himself on the world stage.

The Prime Minister, still weeks into the job, is relatively untested in diplomatic matters, having focused almost entirely on domestic issues during his time in government.

His second overseas trip as Prime Minister – after travelling to Egypt for the UN climate talks – will include meetings with US President Joe Biden and other leaders.

He will want to restore Britain’s reputation for reliability despite recent political turmoil and show that he is returning stability to the economy at home in the wake of his predecessor Liz Truss’s disastrous mini-budget.

– What bilateral meetings will the PM have?

Mr Sunak has one-on-one meetings scheduled with leaders including Mr Biden, India’s Prime Minister Narendra Modi, Japan’s premier Fumio Kishida, new Australian Prime Minister Anthony Albanese, Indonesian President Joko Widodo and Saudi Arabia’s Crown Prince Mohammed bin Salman.

The Prime Minister’s official spokesman said “there will be a wide range of issues to discuss” with Mr Biden in their first in-person encounter.

“We talked about AUKUS before as an example of the close partnership work but most pressingly will be our continued very close co-operation on Ukraine, where we are working hand in glove,” he said.

Mr Sunak will want to soothe any concerns Mr Biden, the US President with proud Irish heritage, has about Brexit’s threat to the Northern Ireland peace process.

With Mr Modi, the Prime Minister will discuss continuing work on “securing a trade deal that works for both countries,” the spokesman said.

– What else is happening?

All eyes will be on a meeting between Mr Biden and China’s leader Xi Jinping, their first in-person talks since the US president took office, expected ahead of the summit on Monday.

It comes amid sour relations between the world’s two largest economies.