BUENOS AIRES, Argentina — World leaders arrived Thursday in the Argentine capital for the Group of 20 summit of the globe’s largest economies as issues such as a trade war between the United States and China, the killing of a Saudi journalist in the country’s Istanbul Consulate and the conflict over Ukraine threatened to overshadow the gathering.

The two-day summit beginning Friday is supposed to focus on development, infrastructure and food security, but those seemed largely an afterthought amid soured U.S.-European relations and as the United States, Mexico and Canada hammered out the final language of a replacement for the North American Free Trade Agreement expected to be signed Friday.

Michael Shifter, head of the Inter-American Dialogue, a Washington-based think tank, said that this G-20 summit was once considered an opportunity for Latin American members Argentina, Brazil and Mexico “to project a regional bloc to shape a global agenda.”

But, he said, “that turned out to be a fleeting aspiration.”

“The fact that the G-20 is taking place in South America for the first time is almost beside the point,” Shifter said. “Argentine President Mauricio Macri, the summit’s host, has lowered expectations. … Now a success would be a summit meeting that goes smoothly, without any major disruption.”

Nonetheless, French President Emmanuel Macron, who flew into Buenos Aires on Wednesday as one of the earliest arrivers, clung to the importance of the ideal of cooperation that the G-20 represents.

“I believe in our capacity to make the spirit of dialogue and cooperation triumph,” Macron said at a joint news conference with Macri, warning that if nations “close down,” the alternative could be trade wars or armed conflict.

Macron also called for international involvement and “complete clarity” in investigations into the killing of dissident Saudi journalist Jamal Khashoggi, and said European leaders should discuss it at a meeting Friday.

Macri said the matter of the killing would be “on the table” during bilateral and possibly broader meetings.

Saudia Arabia has denied that Crown Prince Mohammed bin Salman played a role in Khashoggi’s gruesome slaying. But Human Rights Watch accuses him of responsibility and also of war crimes in Yemen, and on Wednesday, Argentine legal authorities took initial action to consider a request to prosecute him for alleged crimes against humanity, a move apparently aimed at embarrassing him as he attends the summit.

It is to be bin Salman’s first significant appearance overseas since the killing. Turkey’s Recep Tayyip Erdogan, who has been sharply critical of Saudi Arabia over the incident, is also in attendance.

“Given the role that Turkey has played in this, given that the murder happened at the Saudi consulate in Istanbul, this will be an interesting meeting,” said Willis Sparks, director of global macro politics at Eurasia Group. “Just to see how leaders interact with the crown prince will be interesting — how warm they are. I expect (U.S. President Donald) Trump to be very warm with him, but European leaders probably are going to be very reluctant to have their pictures taken with him.”

An expected high-profile bilateral meeting between Trump and Russia’s Vladimir Putin planned for Saturday was abruptly canceled by Trump, who made the announcement in a tweet citing Russia’s seizure of Ukrainian vessels over the weekend.

The Kremlin said it had not been notified and only learned about it from the tweet. Russian news agencies quoted Putin spokesman Dmitry Peskov as saying the cancellation means that Putin will have “a couple more hours” for “useful meetings” with G-20 leaders.

Trump was still scheduled to meet with Chinese President Xi Jinping, but analysts were not optimistic about prospects for a major breakthrough on the two countries’ trade disputes a month before U.S. tariffs on Chinese goods are set to ramp up.

Shannon O’Neil, an expert on global trade at the Council on Foreign Relations, said she believes it “very likely” that the tariffs will take effect in January.

“I think this is an issue that Trump cares a lot about and is going to use when he campaigns for 2020,” O’Neil said. “It used to be Mexico and NAFTA, and now it’s going to be China.”