NEW YORK • China and Russia's trade relationship has become more complicated since the war in Ukraine started more than three weeks ago, raising questions about the future flow of energy, metals and crops between the two powerhouses.

Before the war, Russia's importance to China as a supplier of raw materials was only growing. That was solidified in the "no-limits" friendship announced between the two nations ahead of the Winter Olympics in Beijing.

Immediately after the invasion, Chinese officials said they disagreed with unilateral sanctions on Russia and would continue normal trade relations with Moscow. But, since then, banks have paused financing purchases and traders are grappling with logistics, while more recently China's Foreign Minister said Beijing does not want to be affected by sanctions.

The biggest trade opportunities may be in energy. The growth in China's economy means the country has an ever-expanding need for coal and gas to heat homes and power factories. Russia is now the second-largest shipper of coal to China after Indonesia, while its gas exports have grown considerably since the Power of Siberia pipeline began flowing in 2019.

Crude shipments have also ticked higher in recent years - including pipeline oil, Russia was the No. 2 supplier to China last year, behind only Saudi Arabia.

Following the invasion, Chinese buyers, and the lenders that finance their purchases, have largely shunned Russian shipments of coal and liquefied natural gas (LNG) as well as crude.

Another issue is logistics. Several Chinese coal importers and Russian miners met this month to discuss boosting volumes, but cited several obstacles, including whether China's renminbi-based cross-border payment system will be usable, as well as issues with transportation capacity and coal quality, according to the China Coal Transportation and Distribution Association.

There is no way that China would follow international companies and exit its Russian energy assets, said Dr Neil Beveridge, a Hong Kong-based senior energy analyst at Sanford C. Bernstein. "China has this huge growth opportunity for Russia."

Under those circumstances, it would be odd for China to cut back on Russian LNG purchases over the longer term.

But the outlook for coal is entirely different. Russian sales are almost a rounding error compared with the four billion tonnes of fuel mined domestically, and Beijing's plan to raise the capacity of its coal industry by 300 million tonnes would suggest it is seeking to enhance its energy security by doing away with imports entirely.

Rising transportation costs are also the likely impediment to Moscow expanding its grain sales.

Russia sells wheat to more than 100 countries, but China has been one of the few big markets it has struggled to crack. Until recently, shipments were limited because most Russian wheat was banned due to fungus concerns.

Last month, China gave the green light to import wheat from all over Russia as part of the raft of deals sealed during Russian President Vladimir Putin's visit to Beijing. The move was expected to challenge sales from the likes of France, Australia, Canada and the United States.

But even though the restrictions have been lifted, China is likely to continue importing from its usual sources, said Mr Darin Friedrichs, co-founder and market research director of Sitonia Consulting in Shanghai.

"I don't think it's feasible to import huge amounts from new sources like Russia. They will have to pay more," he said.

For some metals, China's dependency on Russia has only weakened in recent years. Indonesia has, meanwhile, emerged as its main supplier of nickel.

And even though Russia's share of refined copper imports has risen, the expansion of China's smelting industry means that the import of ore directly from miners in places such as South America has become more important.

In any case, China is already buying most of Russia's refined copper exports, according to a recent note from UBS, which suggests the upside is limited.

For palladium, which is chiefly used to cut car pollution, Russia's exports to China have increased in recent years, and could theoretically rise further. A potential obstacle, according to UBS, is that companies listed in Europe produce most of the catalytic converters sold in China, and they may not want Russian supply.

BLOOMBERG