Starbucks Coffee Co said on Friday it would raise the price of its packaged coffee by an average of 12 percent after its Chief Executive Howard Schultz once again blamed speculators for pushing coffee prices higher.

I think it's artificial. I think financial speculation has really stepped into the market, Schultz said, adding that coffee drinkers would not respond positively to higher prices.

I think it's a very hard dialogue with the consumer, face to face, as we have to as a retailer, when in fact there probably isn't a substantive answer, Schultz said.

Shares of Starbucks, the world's biggest coffee shop chain, closed down 13 cents, or 0.4 percent, at $34.96.

The price increase will affect Starbucks and Seattle's Best Coffee brands, It is the company's first price increase on grocery packaged coffee since March 2008.

Starbucks raised prices last year on some drinks in its cafes.

May arabica coffee futures increased 5.30 cents on Friday to finish at $2.762 per pound. The arabica market was up 0.65 percent on the week.

Analysts said tight supplies of high-quality washed arabica beans had bolstered the market. Short-covering boosted arabicas because investors were nervous ahead of the weekend with fighting in Libya and the crisis in Japan.

Every supplier that I talk to, every producer, first thing I ask is, 'Is there any problem with supply and demand?' Schultz said at the National Coffee Association meeting on Friday. He said they answer no.

Global stocks are at the lowest level since the International Coffee Organization began keeping records in 1965. The ICO has said stocks could fall lower.

Many roasters have passed along higher costs to consumers. Most recently, Kraft Foods raised its list prices for most of its Maxwell House and Yuban roast coffees by 22 percent, its fourth and biggest increase in the past year.

Last month, J.M. Smucker Co raised the price of Folgers brand coffee by 10 percent.

(Additional reporting by Lisa Baertlein in Jamestown, R.I., Jessica Wohl in Chicago and Phil Wahba in New York)