CHICAGO -- While Xi Jinping and Donald Trump grab headlines for sparring over broad trade and technology issues, another Sino-American battle is brewing over who has the fastest supercomputer.

Just days before Trump was due to meet China's president at the G20 meeting in Osaka, Washington imposed restrictions on five Chinese supercomputer companies which bar them from buying U.S. technology. The move was widely seen as a U.S. attempt to hinder China's development of supercomputing capability, which promises big benefits to the military, artificial intelligence and other fields.

The move came as scientists in the two countries push supercomputer calculation speeds to new highs. In March, the U.S. Department of Energy said Aurora, the first exascale supercomputer in the U.S., will go online in 2021 at the Argonne National Laboratory near Chicago.

China, which has more supercomputers than any other country, aims to bring its own exascale computer into operation by 2020, and Japan intends to follow in 2021.

An exascale computer can make 1018 calculations per second. That is equivalent to every man, woman and child on Earth making 150 million calculations per second simultaneously, according to the Argonne laboratory.

For now, the U.S. maintains a technological lead, judging by the latest ranking. The U.S. has five of the 10 fastest supercomputers in the world, while China has two, the June ranking by Top500 shows.

But China remains a potent force, and experts predict it will eventually overtake the U.S. again. High-performance computers form part of Beijing's Made in China 2025 program of industrial advancement.

It remains to be seen what if any impact the placement of Chinese companies on a U.S. technology export blacklist will have on China's supercomputer programs, and whether more names will be added.

Aurora will be built by chipmaker Intel and supercomputer manufacturer Cray, both U.S. companies. The hardware is likely to be used in astronomy research, personalized medicine and solar power development.

Argonne, about a 45-minute drive southwest from Chicago, looks like a university campus, with buildings situated on 6 sq. kilometers of parkland. A new building to house Aurora is under construction.

The laboratory, which is operated by the University of Chicago, was founded in 1946 and is one of 17 such facilities overseen by the Department of Energy. It had its origins in Enrico Fermi's Manhattan Project, which created the world's first controlled nuclear chain reaction.

Michael Papka, a senior scientist sporting an impressively long goatee, is director of the Argonne Leadership Computing Facility. One of the tools at his disposal is Mira, currently No. 24 in the global supercomputer speed contest. If all goes according to plan, Aurora will be 100 times faster.

Papka said there is an urgent need to upgrade supercomputer performance. In the past, such devices were mostly used in basic research. But in recent years, demand for processing power has soared in fields ranging from artificial intelligence, to data analysis, to applied engineering. The machines now in operation can hardly keep up with demand.

Michael Papka, a senior scientist at the Argonne National Laboratory near Chicago, shows off the inside of the Mira supercomputer. The Aurora supercomputer is expected to be 100 times faster.

The development of next-generation supercomputers in the U.S. dates back to 2015, when President Barack Obama issued an executive order creating the National Strategic Computing Initiative. The goal was to maintain and extend U.S. leadership in high-performance computing.

The initiative was launched by the Department of Energy, the Defense Department and the National Science Foundation. After President Donald Trump took office, three Department of Energy laboratories began competing head to head to build the country's first exascale supercomputer.

Jack Dongarra, a professor at the University of Tennessee and a founding member of Top500, which ranks the world's fastest supercomputers, said that in addition to Argonne's Aurora, the Department of Energy plans two more exascale supercomputers. The Oak Ridge National Laboratory is scheduled to have Frontier operating in 2021, while the Lawrence Livermore National Laboratory is slated to build El Capitan in 2022.

But things may not go according to plan, Dongarra said, adding that Argonne may not be the first to succeed.

Top500 publishes its list of the world's fastest supercomputers twice a year, in June and November. Although the U.S. held a huge lead when the ranking began in 1993, China has outpaced it over the past decade or so.

China took the top spot for the first time in November 2010 with the National University of Defense Technology's Tianhe-1. The U.S. regained the lead briefly, but the Tianhe-2 and the Sunway TaihuLight held the top spots from 2013 to 2017. China overtook the U.S. in total supercomputers in 2016.

The fastest U.S. machine fell to the third place in 2016, and to fifth place by November 2017. But in June 2018, the Oak Ridge National Laboratory's Summit regained the top spot. As of November last year, the U.S. was home to five of the 10 most powerful supercomputers in the world.

China showed a slowdown in quantity, with 219 of the world's 500 most powerful supercomputers, down from 227 in November. The U.S. increased its number to 116 from 109.

On June 21, the U.S. Department of Commerce announced the placement of five Chinese supercomputer-related business entities on its Entity List, saying they pose a threat to the national security of the U.S. The five blacklisted organizations include Dawning Information Industry, better known as Sugon, and an affiliate forming a joint venture with U.S. chipmaker Advanced Micro Devices. Placement on the list makes them ineligible to receive exports of semiconductors and other U.S. technology.

The Trump administration in May put Huawei Technologies on the same list. This followed the imposition of an export ban on Chinese chipmaker Fujian Jinhua Integrated Circuit, last October.

After last weekend's Group of 20 summit in Osaka, White House economic adviser Larry Kudlow told Fox News that Huawei will remain on the Entity List. He also said no licenses will be granted that would allow Huawei to obtain U.S.-made equipment in cases that might pose a national security risk.

Next-generation supercomputers have the potential to fuel groundbreaking innovations, contributing to research in cosmology, genetics, the human brain, new materials and energy, to name a few. They have important implications for both industry and national security.

China is now building three pre-exascale supercomputers and is expected to have an exascale supercomputer operating in 2020, ahead of the U.S., Dongarra said, adding that he believes China will gain superiority over the U.S. in the long run.