World leaders have descended on Buenos Aires for the two-day G20 summit.

The summit of the globe’s largest economies began Friday. But before it even got started, drama between some nations attending the gathering escalated.

President Trump, who left for the summit Thursday, already sign a revised North American trade pact with Canada and Mexico. And ahead of his arrival in Argentina, he abruptly canceled a sit-down with Russian President Vladimir Putin.

Read on for a look at what to know about the summit.

The setting

For two days, the leaders of nearly two dozen nations will convene in Buenos Aires, Argentina for the G20 summit.

It is the first time the summit has taken place in South America. It was held in Germany last year.

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The summit was founded in 1999 as a forum of central bank presidents and finance ministers, according to its website. It began to include heads of government in 2008 during the international financial crisis.

According to the Financial Times, the host country could be seen as more vulnerable as the Argentine peso was devalued in recent months.

The participants

Along with host nation Argentina, the participants include Australia, Brazil, Canada, China, the European Union, France, Germany, India, Indonesia, Italy, Japan, Mexico, Russia, Saudi Arabia, South Africa, South Korea, Spain, Turkey, the United Kingdom and the United States.

Regional groups represented by Rwanda, Senegal and Singapore are also invited, as is Jamaica on behalf of the Caribbean Community (CARICOM).

Additionally, the host nation is able to invite other guests. Argentina invited Chile and the Netherlands this year.

The plan

The weekend is packed with meetings divided into two “channels."

Meetings in the financial channel feature central bank presidents and finance ministers to discuss “global collaboration in financial and monetary policies, which may include issues such as investment in infrastructure, fiscal policy, inclusion and financial regulation.”

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The second channel is the “Sherpas channel” which includes a variety of non-financial topics such as gender quality or energy.

The summit also encourages participation in “affinity groups” that deal with business, labor, youth and science, among other things.

Since the presidency of the summit changes each year, Argentina will participate in what is called a “troika” with last year’s president (Germany) and next year’s (Japan) to ensure “continuity in the group’s agenda.”

Trump joined Canadian Prime Minister Justin Trudeau and outgoing Mexican President Enrique Pena Nieto to sign a revised North American trade pact that he called "groundbreaking" and a benefit for "working people." The U.S.-Mexico-Canada Agreement is meant to replace the 24-year-old North American Free Trade Agreement, which Trump has long denigrated as a "disaster."

The drama

“The G20 Leader's Summit is at risk of falling into disarray with the summit being overshadowed by items not on agenda, such as the United States and China trade war, Russia's aggression against Ukraine and the presence of the Saudi crown prince,” Thomas Bernes of the Centre for International Governance Innovation, a Canada-based think tank focusing on global governance, told The Associated Press.

“The true test will be whether the other members of the G20 will act resolutely or whether will we witness the crumbling of the G20 as a forum for international economic cooperation.”

Ahead of the summit, Trump nixed a meeting with Putin, citing the seizure of Ukrainian ships and crews in the Black Sea by Russia.

“Based on the fact that the ships and sailors have not been returned to Ukraine from Russia, I have decided it would be best for all parties concerned to cancel my previously scheduled meeting in Argentina with President Vladimir Putin,” Trump announced in a tweet. “I look forward to a meaningful summit again as soon as this situation is resolved!”

Then there’s the brouhaha surrounding Mohammed bin Salman, the Saudi crown prince. He’s been accused of war crimes in Yemen and responsibility for the gruesome slaying of newspaper columnist Jamal Khashoggi inside the Saudi consulate in Istanbul last month. The kingdom has denied he played a role in the murder.

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Argentine legal authorities took action to consider a request from Human Rights Watch to prosecute him for alleged crimes against humanity, a move apparently aimed at embarrassing him as he attends the summit. Argentine President Mauricio Macri said the killing would be “on the table” during bilateral meetings during the summit.

Trump, on the other hand, has been widely criticized for his response to the killing.

And some European leaders at the summit are facing domestic struggles at home. French President Emmanuel Macron has faced massive protests over rising fuel taxes. Britain’s Theresa May is fighting for political survival as she tries to pull her country out of the EU. And Italy’s Giuseppe Conte heads up a populist coalition that is clashing with the EU and suffers internal divisions.

Fox News’ Adam Shaw and The Associated Press contributed to this report.