Green Mountain Coffee Roasters Inc. again extended a tender offer for a third time as it attempts to acquire Diedrich Coffee Inc., the company said Tuesday.

The offer by Green Mountain subsidiary Pebbles Acquisition Sub Inc., which was set to expire on Monday, has been extended until May 3. The 20-day extension is the maximum allowed under the companies’ acquisition agreement.

About 2.8 million shares have been tendered in the offer as of Monday.

In February Green Mountain extended its offer by 20 days after approximately 2.3 million shares had been turned in for $35 each.

Diedrich Coffee Inc., based in Irvine, Calif., is backing the takeover and has about 5.7 million shares outstanding.

Regulators in January asked for more information about the deal. It was the second time the U.S. Federal Trade Commission asked for more details.

Before Green Mountain put in a bid, Peet’s Coffee and Tea said it would buy Diedrich. Green Mountain, however paid an $8.5 million termination fee to end that deal and extend its own shopping spree.

Green Mountain bought Tully’s Coffee brand and a wholesale coffee business from Tully’s Coffee Corp. in March 2009 for $40.3 million. It bought Toronto specialty coffee company Timothy’s in November for $157 million, including the Timothy’s World Coffee brand and wholesale business but not the retail operations.

Green Mountain shares rose $1.66 to $98.60 in afternoon trading Tuesday while shares of Diedrich slipped 11 cents to $34.70.