The sources, who were not authorized to speak publicly on the issue, called IBM's examination of Sun's assets standard procedure. They added that any deal is unlikely to be reached before next week at the earliest.
CNBC, citing a Wall Street Journal report, said earlier on Friday that International Business Machines Corp's due diligence process was holding up the Sun deal.
IBM is examining the terms of Sun's various technology licenses to check for any conflict with IBM's business, the Journal reported on its website.
Sources on Tuesday told Reuters that IBM was in talks to buy Sun. The Journal, which first reported the negotiations, said the deal could be worth $6.5 billion to $8 billion.
Sun shares closed Friday's session down 6.1 percent at $8.10 on the Nasdaq, giving the company a market value of about $6 billion based on about 745 million shares outstanding as of January 30.
IBM shares closed down 0.16 percent at $92.51 on the New York Stock Exchange.
(Reporting by Ritsuko Ando and Anupreeta Das; Editing by Gary Hill)