Companies are marketing at least $18 billion of bonds in the U.S., heading for the busiest day in a month, with investment-grade yields at record lows.

Royal Philips Electronics NV, the world's largest maker of patient-monitoring systems, plans to sell a two-part offering, according to a person familiar with the transaction, who declined to be identified because terms aren't set. Bombardier Inc., the maker of aircraft and rail equipment, is planning to sell $500 million of 10-year notes, according to another person with knowledge of that transaction. DirecTV, the biggest U.S. satellite television service, may sell $4 billion of five-, 10- and 30-year debt.

Europe's fiscal crisis has stoked demand for the perceived safety of dollar-denominated investments from fund managers wagering that global banking system strains won't curb U.S. economic growth.