SYDNEY, March 14 (Reuters) - Singapore Airlines is preparing to issue a 10-year dollar bond that could raise at least $300 million, according to three sources with direct knowledge of the matter.

Initial price guidance for the deal has been set at the 10-year U.S. Treasury rate plus 150 basis points, a term sheet seen by Reuters showed. The size of the deal could reach $500 million, one of the sources added.

The sources could not be identified discussing confidential information.

"At this juncture, a 10-year U.S. dollar bond issuance looks attractive," a Singapore Airlines spokeperson said, adding the company regularly reviewed its funding requirements versus its existing cash position.

Orders worth more than $1 billion have been lodged on Thursday by potential investors, a book message sent by the deal's bankers showed. (Reporting by Scott Murdoch in Sydney and Yantoultra Ngui in Singapore; Editing by Kim Coghill)