SEATTLE — Apple Inc.’s stock flirted with $300 Tuesday as investors high on the iPad’s promise pushed shares to a record peak. Analysts see few reasons to believe shares will stop there.

As was the case with the iPhone, Apple’s iPad is setting the standards for this generation of tablet computers as competitors scramble to match the design and functions.

So far, no credible challengers have hit the market. Microsoft Corp. CEO Steve Ballmer has promised Windows-based tablets, but so far there are no solid details. Meanwhile, tablets based on Google Inc.’s Android system are starting to emerge, but they have smaller screens than the iPad’s.

In the first quarter it was available, Apple sold 3.3 million iPads.

Rajesh Ghai, an analyst for ThinkEquity LLC, said he believes Apple sold 5.7 million iPads in the most recent quarter, which ended in September.

He said that adds about $3 billion in revenue – not bad for a product category that didn’t exist before April. Analysts’ estimates for iPad unit sales in 2011 are in flux, with those on the conservative end putting the number around 20 million while more bullish forecasters say it could be 50 million.

A few other factors are bolstering investors’ enthusiasm for Apple, which reports its quarterly results on Monday. The Cupertino, Calif.-based company is planning a big push in China, with 25 retail stores expected to open there by the end of next year.

There’s also the new slate of iPods, which Apple unveiled in September, in time for the profitable gadgets to make their way onto holiday shopping lists. And investors may be choosing to believe increasingly loud buzz that Verizon Wireless will get its own version of the iPhone in 2011. Shares in Apple traded as high as $299.50 Tuesday before ending the day at $298.54, a gain of $3.18.