Some leaders from the Group of 20 major economies have expressed fears about the potential negative impact of a U.S.-China trade war on the world economy at a session of their two-day summit that started on Friday, a Japanese government official said.

But it remains to be seen whether the G-20 can agree on a joint communique, as the United States and China, the world's two largest economies, have been engaged in tit-for-tat rounds of punitive tariffs on hundreds of billions of dollars of each other's imports.

At the Asia-Pacific Economic Cooperation summit earlier this month, leaders of the 21 members failed to finalize a joint declaration for the first time since the forum began in 1993, against a backdrop of the deepening divide between Washington and Beijing.

If the G-20 summit also falls short of adopting a joint communique for the first time since its inception in 2008, skepticism would grow about the ability of the current international framework to find common ground, blurring the outlook for the global economy.

On the sidelines of the G-20 gathering, designed to concentrate on fiscal and monetary policy matters, U.S. President Donald Trump and Chinese President Xi Jinping are slated to hold their first face-to-face talks since November 2017.

At the outset of his meeting with Japanese Prime Minister Shinzo Abe in Buenos Aires on Friday, Trump voiced optimism about the prospects of the planned U.S.-China summit, saying, "We're working very hard."

"If we can make a deal, that'd be good. I think they want to, I think we'd like to," Trump said, adding, "There's some good signs. We'll see what happens."

During a meeting with Xi in the capital of Argentina, Abe said he hopes that the U.S. and Chinese leaders will have a fruitful discussion, according to the Japanese official.

Citing U.S. and Chinese officials, the Wall Street Journal reported Thursday that the two sides are considering launching new talks looking at "big changes" in Chinese economic policy in return for Washington holding off on further tariffs through the spring.

Speculation, however, is rife that the two leaders will not easily make concessions over trade issues, as Trump has continued his threats to take additional measures against China despite Xi's eagerness to resolve the ongoing trade dispute through dialogue.

So far, the United States has imposed tariffs on $250 billion of Chinese imports -- or about half the goods it imports from China each year -- in response to Beijing's alleged theft of intellectual property and technology, as well as other trade complaints.

In retaliation, China has levied tariffs on more than 80 percent of all goods imported from the United States.

"We need to safeguard the multilateral trade system by adhering to the spirit of openness and cooperation," Xi was quoted by Xinhua News Agency as saying at a session of the G-20 summit on Friday.

Trade problems "should be widely debated" and each nation "should not become dogmatic," Xi told his G-20 counterparts, according to the state-run media.

Criticism, meanwhile, has been lingering among the international community about Beijing's alleged unfair business practices. China has also been lambasted by many G-20 countries for providing opaque benefits to state-owned firms.

Trump has apparently been attempting to not only curb massive U.S. trade deficits with China but also to sell U.S. products in Chinese markets without concern about intellectual property and technology theft, diplomatic sources said.

In addition to U.S.-China trade tensions, the G-20 leaders discussed at the summit Russia's annexation of Ukraine's Crimea region and the murder of Saudi journalist Jamal Khashoggi, the Japanese official said, although he declined to disclose any details.

On the economic front, the G-20 nations are expected to have exchanged views on other risks to the world economy, including the slowdown of China's economy, and U.S. monetary policy normalization that could trigger an outflow of capital from emerging markets.

Currency policy may have cropped up, too, as Washington has been dissatisfied with the recent depreciation of the yuan giving an advantage to Chinese exports.

The G-20 groups Argentina, Australia, Brazil, Britain, Canada, China, France, Germany, India, Indonesia, Italy, Japan, Mexico, Russia, Saudi Arabia, South Africa, South Korea, Turkey, the United States and the European Union.