A federal judge in Alexandria has rejected a suit by three low-income Arlington women who asked him to force Agriculture Department officials to change a food stamp regulation the women contend is discriminatory and unfair.

Judge Richard L. Williams said in his ruling that although the disputed regulation kept some Arlington residents from receiving as much food stamp aid as othe residents, the regulation could not be changed because it reflected the intent of Congress.

Charles Sabatino, a staff attorney with Legal Services of Northern Virginia, which filed the suit against the Agriculture Department and Virginia welfare officials, said he expects to appeal. The suit claimed that more than $10,000 a month in federal funds are withheld from Arlington residents because of the regulation.

State and federal officials agreed the regulation was the result of a classic lack of coordination between local and federal welfare bureaucracies. The problem, officials said when the suit was filed last Nov. 28, is that some low-income residents receive an average of $160 per month under a federal rent assistance program, money which does not count as income when food stamp benefits are calculated.

But welfare money distributed by the county under a similar program is counted as income, reducing the amounts of food stamps that some Arlington residents can receive.

In his opinion, dated Monday, Williams wrote that he was "sympathetic" to the women, but he "cannot disturb" to the regulation because it had been passed by Congress.