Apple is set to announce its fiscal year 2012 first-quarter earnings later today, and analysts are expecting record iPhone sales due largely in part to the release of the iPhone 4S and holiday push.

Earlier this month, Piper Jaffray analyst Gene Munster raised his iPhone estimate for the holiday quarter to 30 million, up from 26 million previously.

This will be the iPhone 4S’s first full quarter on the market since its release in early October. While the 4S saw a tepid initial reception, the fact that the iPhone is now carried by all three major U.S. operators, as well as regional carrier C Spire, could mean total sales for the quarter will exceed expectations.

Analysts will also be closely watching sales of the iPad, following the release of Amazon’s Kindle Fire and Barnes & Noble’s Nook Tablet.

In research notes from earlier this month, Morgan Keegan analyst Tavis McCourt trimmed his estimates for Apple’s fiscal first quarter that ended last month after concluding that the iPhone probably sold better than he thought, but that the Kindle Fire probably stole a couple of million units worth of sales from Apple’s iPad.

McCourt said he expects iPad revenues to generate 21.3 percent of revenues in the December quarter for Apple, up from 17.2 percent in the year-ago period, although down from 24.3 percent in the previous quarter.

“We are lowering our unit shipment estimates for iPad in the Dec. quarter from 16 million to 13 million. Based on data from Amazon, we believe the Amazon Fire likely sold 4-5 million units this holiday season, which probably means maybe 1-2 million cannibalized iPad sales at most,” McCourt wrote.

Shares of Apple were down slightly in early morning trading from an all-time high of $425.10 to $423.16. Apple is set to report its earnings after market close at 5 p.m. Eastern time today.