The company, 45% owned by mining group Anglo American, shut many of its mines early this year after a sharp fall in diamond prices during the economic downturn and posted a 99% plunge in first-half net profit in July.

“The shareholders of De Beers ... have agreed in principle, and subject to satisfactory refinancing terms of the company’s existing debt, to further investment in De Beers by way of a rights issue,” it said in an emailed statement.

Anglo, South Africa’s Oppenheimer family, which holds 40%, and the Botswana government, with 15%, have not yet indicated if they plan to take up their full rights, spokeswoman Lynette Gould said.

The shareholders would likely wait to see the terms of refinancing of the firm’s $1.5 billion debt facility before making a decision, she added.

On Friday, De Beers said it expected banks to renew that facility before it came due in March next year.

The diamond group also has a $2 billion debt facility that falls due in 2012.

“By reducing De Beers’ level of external debt and improving its capital structure, this investment would better enable the company to take advantage of new opportunities and demonstrate the shareholders’ confidence in De Beers’ continued market leadership as the recession gives way to recovery,” De Beers said.

The chief executive of the company’s Canadian wing last week predicted a modest rebound in global demand next year following a tough 2009.

“We’re actually looking at next year probably about 10% or a bit more (increased diamond demand) against where we were this year. So it’s up, but it’s not anywhere near to where we were in 2008 and 2007,” De Beers Canada Chief Executive Gowans told Reuters in an interview.