The working group is evaluating the technical and legal aspects of 156 logging deals, mostly signed during a 1998-2003 war and subsequent corruption-plagued interim government.

A list published in the local press on Wednesday showed only 29 of the contracts met the minimum standards required.

"These are the opinions of the technical working group," Abel Leon Kalambayi, the head of the commission that will make the final decision on the deals, told Reuters.

"They do not bind the commission. We must wait for the end of the process and the commission's recommendations," he added.

Amongst contracts recommended for cancellation are 10 of 16 belonging to Portuguese-owned Sodefor, a unit of NST.

Siforco, a subsidiary of Germany's Danzer Group, had three of its nine logging deals picked out while Safbois saw both of its contracts on the cancellation list.

Together the three companies account for more than 66 percent of all timber exported from Congo, researchers say.

Logging and land clearance for farming are eating away the Congo Basin, home to more than a quarter of the world's tropical forest, at the rate of more than 800,000 hectares a year.

In 2002, with the country partially under the control of rebels, Congo issued a five-year moratorium on new logging contracts to try and stem rampant deforestation.

The measure went largely unheeded and companies continued to sign new deals.

Conservation campaigner Greenpeace said Wednesday's findings did not go far enough and accused the working group of not living up to its own published criteria for evaluating the deals, which require compliance with the moratorium.

"The fact that 16 titles out of the 29 that have received a favorable opinion have been obtained in clear violation of the 2002 moratorium is completely incomprehensible," Judith Verweijen, Africa Policy Advisor for Greenpeace, told Reuters.

The review commission is expected to publish its preliminary findings in mid-September. (For full Reuters Africa coverage and to have your say on the top issues, visit: http://africa.reuters.com/) (Editing by David Lewis and Mary Gabriel)