Apple’s $1 billion of floating debt due 2016 may pay 5 basis points, or 0.05 percentage point, more than the three- month London interbank offered rate, with a $2 billion, five- year floater potentially yielding 25 basis points more than the benchmark, said the person familiar with the offering.

The $1.5 billion of three-year, fixed-rate debt may pay 20 basis points more than similar-maturity Treasuries; $4 billion of five-year notes may have a relative yield of 40 basis points; $5.5 billion of 10-year securities may have a spread of 75 basis points and $3 billion of 30-year bonds may pay 100, said the person, who asked not to be identified because terms aren’t set.

Libor, the rate at which banks say they can borrow in dollars from each other, was set at 0.273 percent today.

No AAA

While Apple’s $145 billion of cash is more than the combined funds of every AAA rated U.S. company including Microsoft, it failed to win the bond market’s highest credit grade from Moody’s Investors Service and Standard & Poor’s. Moody’s rated the firm Aa1 with S&P giving it a grade of AA+.

That rating tier is “inconsistent” with Apple’s credit risk, according to Fitch Ratings, which yesterday said the company’s “significant liquidity cushion” was overshadowed by the threat of volatile consumer preferences, significant competition and rapid technology changes. While Fitch hasn’t released a public grade for Apple, it said such a ranking would likely fall “at the highest end” of the single-A tier, lower than where Moody’s and S&P graded the debt.

Microsoft, along with Johnson & Johnson, Exxon Mobil Corp. and Automatic Data Processing Inc., is rated Aaa by Moody’s and AAA at S&P.

Concern that Apple’s pace of sales growth is slowing were reinforced last week by a forecast for narrowing gross margins and sales this quarter that may miss analysts’ predictions by as much as $4.9 billion. Apple had its first profit decline in a decade last quarter amid accelerating competition in mobile devices from Samsung Electronics Co.

Returning Cash

Using new debt to finance Apple’s $55 billion addition to its plan to return cash to shareholders through 2015 with buybacks and dividends may require annual issuance of between $15 billion and $20 billion, Ping Zhao, an analyst at CreditSights Inc. in New York, wrote in a report April 23. Apple would probably receive a “very attractive rate” for as much as $50 billion in new debt, Barclays Plc analyst Ben Reitzes wrote in a report last month.