China's long-awaited nationwide carbon trading scheme is likely to be ready by the end of 2016 or early 2017, an official with the country's top economic planner said on Wednesday.The country is aiming to bring its emissions to a peak around 2030 and has pledged to make full use of market mechanisms to meet targets.

Seven regional pilot exchanges are in operation and the aim is to extend coverage to the rest of the country by 2016.

"There is a lot of work to be done if we are to get the market running by 2016, and the launch date depends on the progress we make," said Wang Shu, a climate change official with the National Development and Reform Commission (NDRC).

"I personally think it is more practical to set up the market in 2017 but the final say is up to the top authorities," he told Reuters on the sidelines of a conference.

Wang told the conference that the nationwide scheme would be included in commitments due to be submitted to the United Nations before the end of this month, ahead of talks on a new global climate pact in Paris later this year.

Concerns have been expressed that China is rushing into carbon trading without laying the necessary legal and regulatory foundations.

Wang Huitong, a researcher with the Central University of Finance and Economics, told a conference in Beijing on Monday that China should first resolve the problem of permit oversupply.

The exchanges in Guangdong and Hubei provinces and municipalities such as Beijing, Tianjin and Shanghai have been operating for at least a year but trading activity has generally been slow, with companies covered by the scheme having little incentive to buy.

Regulators were reluctant to impose too much of a burden on firms during the first trading phase and handed out most permits for free.

An economic slowdown has lowered industrial output, easing the pressure on companies to reduce emissions and leaving many with a surplus of permits.

The pilot carbon trading phase is due to end in June 2016 and the launch of any new nationwide scheme would depend on whether China can allocate new carbon targets on a national basis, Wang said.

If those allocations were not completed on time, he said, regulators would probably allow the pilot exchanges to continue trading in local permits.

The seven pilots operate independently and have different trading rules and eligibility criteria. That has made cross-platform trading difficult, and Wang said regulators were currently discussing ways of converting local permits into products that can be traded nationally.