China National Petroleum Corp, the country's largest oil producer and owner of the nation's biggest energy producer, is marketing US dollar-denominated notes, as borrowing costs fall to an almost six-week low.

CNPC General Capital Ltd, a unit of CNPC, is offering three-year securities at a spread of about 135 basis points more than Treasuries, five-year notes at about 160 basis points and 10-year bonds at about 195 basis points, a person familiar with the matter said.

Average yields on dollar notes dropped three basis points to 4.26 percent on Monday, the lowest since Feb 27.