Seahawk Oil International Inc. and its president...

Seahawk Oil International Inc. and its president and founder, Robert S. Friedenberg, have extended their offer to buy a sizable chunk of a struggling Houston oil concern until Aug. 11. The initial deadline expired Monday.

Friedenberg blamed the time lag nurtured by through-the-mail communications with Oxoco Inc. shareholders for the lackluster response received so far on the 10-cents-a-share bid. The Friedenberg-Seahawk partnership, which first made the offer last month, said it would buy up to 2.2 million shares--costing $220,000--to obtain a 25% stake in Oxoco. The partnership said it would buy no less than 1 million shares.

Friedenberg founded Oxoco in 1969, but left 10 years later to start Seahawk. Oxoco has lost more than $100 million in the last 15 months.