In an effort to cool speculation and reassure concerned employes, Israel Cohen, president of Giant Food Inc., yesterday told the company's 18,000 workers, "Our company is not for sale."

The head of the 134-store supermarket chain made his statement in response to a story in The Washington Post Thursday reporting that Cohen said he would be willing to discuss selling Giant Food, if someone came along and offered him $1 billion.

The story also reported that Cohen, 72, is selling 296,000 shares of his Giant stock, worth some $6.2 million, to finance personal activities -- including a new $750,000 condo in Chevy Chase -- and as part of his estate planning.

In a letter to employes, Cohen said, "There are no current discussions regarding the sale of our company. There have been no discussions with interested purchasers in the past . . . . We are not seeking offers for the sale of our company."

Cohen added, "I have every intention of seeing the company continue under the current ownership and management."

Trading in Giant Food stock, which closed Wednesday at $19.63 a share, was held up on the American Stock Exchange yesterday until 12:12 p.m. to give Giant officials time to publicize Cohen's statements. Giant stock opened on a volume of 36,600 shares at $20.25 and sold as high as $20.75. It closed at $20.25, up 63 cents for the day on a volume of 82,800 shares.

In a separate news release, Cohen said, "Since we are not seeking any purchase proposals and have received none, the whole question of a possible sale is irrelevant."

On the possibility of a sale, Cohen was quoted in the Thursday story as saying: "I used to say, 'Never, never,' I don't say that anymore. If someone came along and offered the right kind of price -- 20 times projected earnings -- it would be foolish not to discuss it." A factor of 20 times earnings works out to about $1 billion.

Supermarkets General, the New Jersey firm that operates Pathmark Supermarkets, has been mentioned in speculation as a possible future acquirer of the Giant chain.

After selling about 25,000 shares at a price of $21 a share, Cohen instructed his broker to hold up on the sales when the price fell below $21.