China's leader-in-waiting urged the United States to "curb its tendency of politicising economic issues", state media said Wednesday, after a recent step-up in US criticism of Beijing's trade practices.

Ties between Beijing and Washington have been strained after US lawmakers on both sides of the political aisle, under pressure to spur jobs growth as they enter an election year, heap blame on Chinese policies for their economic woes.

"I hope the United States will... curb its tendency towards protectionism and of politicising economic issues," Chinese Vice President Xi Jinping told former US Treasury Secretary Henry Paulson during a Tuesday meeting in Beijing.

Xi, who is widely touted to take over from President Hu Jintao in 2013, added it was "vital" for China and the United States to strengthen economic and trade ties in the face of a global downturn, the state Xinhua news agency said.

The United States has recently stepped up criticism of what it says are unfair Chinese trade practices in the face of deep US voter anger over high unemployment and the state of the economy.

Some US lawmakers have blamed China's rise for job losses at home -- criticism that Beijing has rejected.

Last month, the US Commerce Department announced it would probe complaints by a firm called US SolarWorld Industries America that China was selling solar cells and panels in the US market at below the cost of production, a claim that angered Beijing.

On Sunday, Xinhua ran a commentary accusing US solar makers of "double standards" by "selectively ignoring the millions of dollars in tax breaks and public subsidies... they themselves received."

Chinese solar panel makers too have rejected the probe, warning it risks "seriously hindering the development of green energy."

There has also been increased criticism from US lawmakers of China's yuan currency, which many say is grossly undervalued and costs US jobs -- which Beijing also refutes.

In October, the US Senate passed legislation that could punish China for its alleged currency manipulation, raising hackles in Beijing, where state media warned it could spark a trade war between the two countries.

US President Barack Obama -- striving for re-election November next year -- said last month Beijing had not done enough to allow the yuan to reach a fair market value and called on a now "grown up" China to act more responsibly.

And last week, a group of 59 lawmakers in the United States urged Obama to open an investigation into China's alleged unfair trade practices in the entire clean energy sector.

In his talks with Paulson, who arrived in Beijing on Monday, Xi also urged Washington to ease restrictions on high-tech exports to China and assist Chinese firms wanting to invest in the United States, Xinhua said.