The United States on Monday hailed key trade talks with China as a success, saying they had made "meaningful, concrete progress" on piracy and market access, but warned more work needed to be done.

US Commerce Secretary John Bryson said China had pledged to better enforce intellectual property rights and give US firms a "level playing field" in strategic emerging industries, in which China vowed to invest $1.7 trillion over five years.

But China's controversial currency controls -- a major thorn in the side of US-China ties -- were not discussed at the meeting of the Joint Commission on Commerce and Trade (JCCT), Bryson said.

"Overall this year's JCCT resulted in meaningful, concrete progress," Bryson told reporters after the negotiations, which he described as "tough".

"At the same time, we have a complex trade relationship and not surprisingly significantly more work yet to do."

This year's meeting in the southwestern city of Chengdu took place against a background of growing rivalry between the world's two largest economies and the turmoil in Europe, which threatens to tip the planet back into recession.

In recent months US lawmakers, under intense pressure to spur jobs growth as they enter an election year, have blamed Chinese policies for their country's economic woes and the atmosphere at the JCCT talks was frosty at the start.

Vice Premier Wang Qishan -- China's top finance official -- said earlier the Asian country had made "positive progress" addressing US concerns and called on the Americans to "avoid politicisation of economic issues".

"An unbalanced recovery is better than a balanced recession," Wang said, referring to the turbulence in Europe and the United States.

Bryson, meanwhile, expressed frustration with China, saying the sides had not made sufficient progress during the first day of talks on Sunday and that it was "time to work hard and deliver results".

"Many in the United States, including the business community and the Congress, are moving towards a more negative view on our trading relationship," Bryson said.

But by the end of the talks, Bryson said China had agreed to set up a special office -- headed by Wang -- to coordinate the enforcement of intellectual property rights.

China also pledged it would create a "level playing field" for US companies investing in strategic emerging industries, such as clean energy, and allow foreign automakers to invest in the green vehicle market without transferring their technology to Chinese enterprises or establishing a local brand.

The two sides also signed agreements including a memorandum of understanding on energy cooperation and an action plan for cooperation on high-tech trade.

Chinese officials -- who had demanded the United States provide equal access for domestic firms investing in the world's economic superpower -- told reporters they had had "frank" discussions with their US counterparts.

Wang said he hoped the US side would "make substantive progress" in relaxing controls on high-tech exports to China and "exercise caution" in taking action against Chinese shipments, a key driver of the world's second-largest economy.

Wang's comments came after he warned on Saturday that China needed to resolve "structural problems" in its financial system to cope with a sustained global recession that threatens its export-dependent economy.

"The one thing we can be sure of is that the global economic recession will last for a long time," the state Xinhua news agency quoted him as saying.

Ties between Beijing and Washington have been strained after a string of US lawmakers on both sides of the political aisle stepped up criticism of China's yuan exchange rate, which they argue is grossly undervalued and costs US jobs.

US President Barack Obama -- facing an election in November next year -- said recently 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.