ROME (AP) — The leaders of Russia and China aren't coming. Turkey nearly set off a diplomatic incident on the eve of the meeting. And the United States, Australia and France will be at the same table for the first time since Washington pulled the rug out from under Paris' $66 billion submarine deal Down Under.

A Group of 20 summit scheduled for this weekend in Rome - the first in-person gathering of leaders of the world's biggest economies since the COVID-19 pandemic started - is not business as usual. That's especially true since as soon as the event ends, a bigger United Nations summit devoted to climate change begins in Glasgow, Scotland.

In many ways, the two-day G-20 meeting is serving as a Roman holiday preamble to the 12-day Glasgow summit, with the climate dossier taking center stage at the new Nuvola (Cloud) convention center in the Italian capital's Fascist-era EUR neighborhood.

Some of the participating presidents and prime ministers met at a COVID-focused Group of Seven summit in July, and some passed one another in the U.N. hallways during the General Assembly in New York last month. But this is the first time the leaders of countries that account for 75% of global trade and 60% of the world's population will be meeting as a group after nearly two years of virus-induced lockdowns.

While economic recovery is a top agenda item, host Italy hopes the leaders will set a shared, mid-century deadline to reach net-zero greenhouse gas emissions and explore a commitment to reduce methane emissions as well.

The United Nations and climate activists also want the G-20 countries to fulfill their longtime pledges of providing $100 billion a year in climate aid to help poor nations cope with the impacts of global warming.

"G-20 members are responsible for over 80% of global emissions. So there is a responsibility when they come together as a group to think about the promise of $100 billion in annual climate financing that is not being met," said Renata Dwan, deputy director of the international affairs think tank Chatham House.

But what can be achieved if the leader of China, the world's No. 1 carbon polluter and No. 2 economy, doesn't show up in Rome?

President Xi Jinping, who hasn't left China since early 2020, is expected to participate remotely, as is Russian President Vladimir Putin. Mexican President Andrés Manuel López Obrador also isn't coming and Japanese Prime Minister Fumio Kishida hasn't confirmed his presence due to a weekend national election.

The absence of Xi and Putin sends a signal that Europe should note in particular, said Massimo Franco, international affairs columnist for Italian daily newspaper Corriere della Sera.

"If China doesn't come to Rome, if Russia -- which has a lot of energy to sell to Europe -- doesn't join the G-20, I think that this G-20 will be a confirmation of European fragility from the energetic point of view," Franco said.

Last month's announcement of a U.S.-British deal to sell nuclear-power submarines to Australia illustrated Europe's geopolitical vulnerability. The deal scuttled France's $66 billion deal to sell French-made diesel-powered submarines to Australia, and led an French government to take the unprecedented action of recalling its ambassadors to the U.S. and Australia.

U.S. President Joe Biden and French President Emmanuel Macron have spoken twice by telephone since the tiff and are expected to meet privately in Rome. Macron is aiming to secure U.S. backing for "the establishment of a stronger European defense, complementary to NATO and contributing to global security," the presidential Elysee Palace said.

Macron has not spoken with Australian Prime Minister Scott Morrison since France's submarine sale went south, however, and it's not clear if the two will meet in Rome.

Carlo Altomonte, a professor of European economics at Milan's Bocconi University, said the U.S.-British-Australian deal was clear evidence of shifting strategic priorities and attention to the Indo-Pacific region to counter China's increased assertiveness, in this case at the expense of Washington's traditional European allies.

"This in a way obliges the European Union to decide, autonomously, a series of local geopolitical questions" at the G-20 level and beyond that until now had long included Washington as the heavyweight partner, Altomonte said.

Turkey, one of the G-20 members, was in a position to cast a pall over the upcoming meeting when it threatened last week to expel the ambassadors of 10 Western nations over their support for a jailed activist. Four of the threatened envoys hailed from G-20 nations Germany, France, Canada and the U.S.

The G-20 also include Argentina, Australia, Brazil, China, India, Indonesia, Italy, Japan, South Korea, Mexico, Russia, Saudi Arabia, South Africa, the United Kingdom and the European Union. Spain holds a permanent guest seat.

Italian Premier Mario Draghi, who helped save the euro with his now-famous promise to do "whatever it takes,'' will have his hands full trying to steer the meeting to nudge some solid climate commitments ahead of Glasgow while negotiating a new era for European multilateralism.

"Not 'whatever it takes,' but I think he'll try to point to the strategic points for Europe, and how Europe can play a role in this mess," newspaper columnist Franco said.

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Sylvie Corbet in Paris, and AP correspondents around the world contributed.

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