A Chinese trade official on Thursday denied a New York Times report that China had banned exports of rare earths to Japan following the detention of a Chinese trawler captain near the Diaoyu Islands.

The report, which was sourced to unnamed industry experts, said an initial trade embargo on all exports of rare earth minerals would last through the end of this month.

"China has not issued any measures intended to restrict rare earth exports to Japan. There is no foundation for that," said Chen Rongkai, a spokesman for China's Ministry of Commerce.

"I don't know how the New York Times came up with this, but it's not true. There are no such measures."

This week, Premier Wen Jiabao threatened further actions against Japan unless it released the trawler captain, whom Tokyo has accused of ramming with two Japanese coastguard ships.

Major rare earths traders in China and Japan told Reuters they had not heard of any ban. One Japanese trade official told Reuters that he had heard rumors of an embargo, but could not comment further.

Rare earths, a group of 17 metallic elements including yttrium and lanthanum used in small quantities to enhance batteries, computer and weapons systems, and other applications, are generally found together.

China is the dominant source of rare earths, accounting for 97 percent of world supply in 2009.

Steep cuts in export quotas for the second half of this year mean that total export quotas for 2010 are about 40 percent below 2009 levels.

"Rare earths export quotas were cut pretty sharply and have been basically used up, you can't export any to Europe or the United States either. People think it's about Japan, but it isn't," said Bruce Zhang, a rare earths expert at consultancy Asian Metal.

"This has nothing to do with the fishing boat incident. The export quotas were issued long before that."

China has gradually over several years reduced exports of rare earths and some minor metals through a quota system designed to keep more of the minerals for its own industry. That effort has been undermined by smuggling, especially through Vietnam.