Intel Corp. (INTC) Thursday gave a sales outlook that fell just below the average analyst estimate, deflating hopes that the world's biggest chipmaker would give a bullish forecast and sending its shares lower.

Intel, which makes the microprocessors found at the heart of nearly 90 percent of personal computers worldwide, said it now expects revenue of $10.4 billion to $10.6 billion, in the middle of its previous guidance of $10.2 billion to $10.8 billion.

"It's going to be viewed as moderately disappointing, not necessarily a structural disappointment, but optimism had definitely become more prevalent with general semiconductor demand overall," said Cody Acree, an analyst with Stifel, Nicolaus & Co.

Intel shares fell 2.5 percent in extended trading after the forecast was issued. The stock fell 1.7 percent to close at $25.70 in regular Nasdaq trading.

The company also reiterated expectations that gross margins would be about 63 percent, but narrowed the range from a "couple points" either way to one point up or down.

"The gross margin guidance is unchanged, and the significance of that is that there are a number of people that may view Intel as having reached peak margins and will view that as a negative," said Bruce Bartlett, director of growth equities at Lord Abbett & Co., which owns Intel stock.

Intel also said capital spending is now expected to come in below the midpoint of its previous forecast of $5.9 billion, and fears of weaker demand sent shares of chipmaking equipment companies down in after-hours trading.

In after-hours trading, Applied Materials Inc. (AMAT) fell as much as 2.7 percent to $18.24 after closing 26 cents lower at $18.73 on Nasdaq. Test gear maker KLA Tencor Corp. (KLAC) shed 2 percent to $50.70 from its close of $51.70.

Intel is expected to earn a net profit of 42 cents per share on revenue of $10.6 billion in the quarter ending December 31, according to Reuters Estimates.

Intel shares have underperformed the broad industry, rising 9.4 percent over the past year, compared to 19.6 percent for the American Stock Exchange Semiconductor Index.