Communications Satellie Corp. announced yesterday that it will proceed with a tender offer to buy up to 2 million shares (20 per cent) of its common stock, despite a Federal Communications Commission order requiring that new funds be set aside for potential refunds to customers.

The FCC also approved yesterday a Comsat request for authority to borrow up to $25 million to finance a portion of the cost of the stock purchase. Comsat said it would extend to Dec. 6 from Nov. 25 the date by which offers may be withdrawn.

Comsat is seeking FCC reconsideration of the refund money order, which the firm said would reduce profits this year by $12.5 million. Trading in Comsat stock was halted on the New York Stock Exchange for a long period yesterday, and when trading resumed at 3:37 p.m. a block of 230,000 shares was traded at $33.50, down $2.625 from Wednesday.

On the Big Board, Comsat closed off $2.875 at $33.25, but in subsequent Pacific exchange trading, it moved up 25 cents a share to close at $33.50 on a nationwide of 270,600 - the fourth most active NYSE issue. Comsat is involved in a dispute with the FCC on its rates for international services - which the regulatory agency contends are too high.