With China embroiled in a trade war with Washington and Russia under Western sanctions, Xi and Putin lashed out at "inequalities" in the global economic system and vowed to pursue closer ties between their countries.

Putin, speaking in front of political and business leaders at the annual Saint Petersburg International Economic Forum, accused Washington of seeking to "extend its jurisdiction to the whole world".

Denouncing the "rhetoric of trade wars and sanctions", Putin called for rethinking the role of the US dollar in global trade and slammed US pressure on both countries.

He pointed to US efforts to block the building of Nord Stream 2, a major new natural gas pipeline from Russia to Germany that would bypass Ukraine, and Washington's pressure on Chinese tech giant Huawei.

"They are attempting not just to squeeze but to unceremoniously push (Huawei) out of the global market," Putin said.

Xi said steps needed to be taken to "overcome inequalities" in the global economic system.

Pointing to Russia as a key partner, he said China was looking to build "beneficial cooperation on the basis of equality and mutual respect" with friendly countries.

"China is ready to share technological inventions with all partners, in particular 5G technology," Xi said.

- Warm personal ties -

Xi arrived in Moscow on Wednesday for a three-day visit with Putin and described the Russian leader as his "best friend" during a meeting at the Kremlin.

The two leaders spoke at the forum on Friday of their warm personal ties, with Xi recounting a boat trip down Saint Petersburg's Neva River they had taken the day before.

The visit comes five years after Moscow's annexation of Ukraine's Crimea peninsula led to a serious rift with the West and a move towards Russia's neighbour to the east.

China meanwhile is locked in a trade war with the United States that has seen Washington impose sweeping duties and move to blacklist companies like Huawei.

Moscow and Beijing's economic ties have grown in recent years, though they remain heavily weighted in favour of China, which dwarfs Russia in economic and demographic terms.

Xi's visit has seen the signing of dozens of commercial contracts in e-commerce, telecoms, gas and other areas.

While this is the Chinese leader's first appearance at the economic forum, where he heads a 1,000-strong delegation, he and Putin have met regularly in recent years.

The partnership is yielding increasing trade, which grew by 25 percent in 2018 to hit a record $108 billion.

But despite political tensions and repeated rounds of sanctions over Moscow's actions in Ukraine, the European Union remains by far the biggest foreign investor in Russia -- well ahead of China and the US.

- Worry over investor arrest -

The first day of the forum on Thursday saw Putin make a pitch for increased foreign investment as Russia looks to revive an economy hit by Western sanctions over Ukraine and the drop in oil prices.

After emerging from recession in 2017, the Russian economy ticked up by only 0.5 percent in the first quarter of this year.

Putin, whose approval ratings have dropped to record lows, has vowed to boost growth through a series of "national projects" -- ranging from healthcare to infrastructure -- that will cost Russia $388 billion.

But foreign investors, already wary of Russia's volatile business climate, were further spooked by the arrest on fraud charges in February of US businessman Michael Calvey, the founder of one of the oldest private equity firms focusing on Russia.

He denies the charges, saying the arrest was the result of a shareholder dispute.

Putin told the forum that investors like Calvey were innocent unless proven guilty and criticised security services for their "unreasonable and sometimes simply illegal interference in the work of businesses."

In a statement through his lawyers on Friday, Calvey regretted that he had been unable to attend this year's forum.

"He expressed regret that it will apparently not be possible for him to attend SPIEF for reasons that are beyond his control," the statement said, with Calvey also thanking the business community "for its remarkable solidarity and support".