Billionaire investor Warren Buffett may buy parts of beleaguered mortgage lender Countrywide Financial Corp, some investors are speculating, according to The Wall Street Journal.

Countrywide's debt-servicing business and its portfolio of mortgages and mortgage-backed securities may be attractive to Buffett, the Journal reported on its Web site on Monday, citing unnamed investors.

Like many mortgage lenders, Countrywide has struggled with rising delinquencies and foreclosures, and an unwillingness among bankers to extend credit, and among investors to buy the loans it makes.

Countrywide, which is being closely monitored by U.S. regulators, sought to reassure investors earlier on Monday that it is safe to do business with the company.

Buffett has been increasing his stake in financial services companies, including those with significant exposure to the mortgage market.

Earlier this month, Buffett's investment company Berkshire Hathaway Inc disclosed an investment in Bank of America Corp, one of the six largest U.S. mortgage lenders, in a regulatory filing.

Berkshire is also a long-time shareholder in Wells Fargo & Co, the second largest U.S. mortgage lender after Countrywide.

Wells Fargo has largely been spared the subprime mortgage-related woes afflicting smaller rivals, helped by its conservative underwriting standards.

Buffett told TV network CNBC last week that the worsening credit and housing markets may present some real investment opportunities.

Berkshire officials were not immediately available for comment. Buffett does not discuss what Berkshire is presently buying and selling.

(Reporting by Anupreeta Das and Jonathan Stempel; editing by Louise Heavens)