Clinton got the non-publicly traded Accoona Corp. stock in 2004, the year the company was created, as a gift for speaking at a company event, The Washington Times reported. Valued at 66 cents a share when issued, he sold the 200,000 shares at $3.50 per share to an undisclosed buyer in May 2006, while the company, backed by the Chinese government, was reporting losses in the tens of millions of dollars.

His wife, Sen. Hillary Clinton of New York, had not announced her intention to seek the Democratic presidential nomination when Clinton sold the stock and plowed the proceeds into the William J. Clinton Foundation, the newspaper said.

The sale was listed on the foundation's tax returns reviewed by the Times. Some ethics experts said they were troubled by the lack of disclosure about the buyer specifically, and the activities of former presidents' foundations generally.

Sheila Krumholtz of the non-partisan Center for Responsive Politics, which studies political money and ethics, said former presidents aren't required to disclose donations and stock transactions to their foundations, but they should to avoid the appearance that money was buying special access.

Accoona, based in Jersey City, N.J., was co-founded by Armand Rousso, who pleaded guilty in 1999 to federal money laundering and other charges. The China Daily Information Co., a subsidiary of the Chinese-controlled newspaper China Daily, holds nearly a 7 percent stake in Accoona.