Intel wrote to customers Wednesday to apologize for continued shortages of the company’s products, acknowledging the shortfall is “creating significant challenges” for PC manufacturers.

The chipmaker reaffirmed the financial forecast it issued a month ago but admitted it continues to struggle to deliver the processors its customers ordered. Intel also hinted at new manufacturing problems.

“I’d like to acknowledge and sincerely apologize for the impact recent PC (processor) shipment delays are having on your business and to thank you for your continued partnership,” Intel marketing Vice President Michelle Johnston Holthaus wrote in a letter to customers posted on Intel’s website.

Holthaus said Intel has endured unspecified “production variability” this fall, which is exacerbating the shortages.

Intel is in the midst of a difficult transition from its current 14-nanometer generation to a new class of 10nm chips. The new chips have suffered from sustained production defects, which delayed their introduction by years.

As Intel finally began moving its factories in Oregon and Israel to make the new 10nm processors this year, that constrained the space available to make the current 14nm chips. Additionally, Holthaus told customers Wednesday that unexpectedly strong PC sales overwhelmed Intel’s production capacity.

The company also said it will use contract manufacturers to produce more chips outside its own factories.

After initially forecasting a decline in sales this year, Intel now expects a modest increase to around $71 billion.

If Intel’s customers are frustrated by the delays, the company’s shareholders don’t appear too concerned. Intel shares closed Wednesday at $57.90, near their highest point since the dot-com era. Intel posted Holthaus’ letter after the markets closed; its stock changed little in after-hours trading.

Intel said in October that it won’t resolve the chip shortages until sometime next year.

The company is in the early stages of a multibillion-dollar construction binge in Oregon, Ireland and Israel to build capacity for new chips manufactured with a new production tool called extreme ultraviolet lithography.

The expansion will enable large-scale production of a future generation of 7nm chips but construction of the additional factory space won’t be complete for at least a couple years.

— Mike Rogoway | twitter: @rogoway | 503-294-7699