WASHINGTON (AP) _ Faced with the threat of a lawsuit from advocates for the homeless, the federal government on Wednesday called off a sales campaign officials hoped would unload 15,000 foreclosed single-family dwellings this weekend.

The campaign had been aimed at building up Federal Housing Administration funds and helping first-time homebuyers get homes at reduced prices, said a Housing and Urban Development spokesman.

The spokesman, Bill Glavin, said all HUD field offices were instructed to cancel a planned weekend promotion of 27,000 of the properties the agency has taken over because owners failed to make payments on them. The homes are still on the market, but the promotion, dubbed the ''coordinated national sales weekend,'' was called off, said Glavin.

''The action is being taken as a result of the threat of litigation by homeless advocacy groups, since any protracted litigation could have an adverse affect on the future sales of foreclosed properties,'' said a HUD announcement.

Roberta Youmans of the National Housing Law Project said her group, which is based in Berkeley, Calif., had written HUD to object to the campaign and threaten legal action. The group assists lawyers helping indigent clients with housing cases.

''We received calls from homeless individuals saying HUD was selling units and they couldn't get them,'' Ms. Youmans said in a telephone interview.

She said many HUD sales result in homes being sold to speculators, and sometimes the homes themselves have been taken away from people who were originally homeless and couldn't make the payments, putting them back on the streets. Others are being rented to people who are rendered homeless by the sales, she said.

''We have a crisis here, with three million families out on the streets,'' Ms. Youmans said.

She said HUD had not formally answered the letter, but advocates for the homeless hope to meet with officials to discuss ways more houses owned by the government might be made available to the homeless.

''The legal issues raised in our letter still remain,'' she said.

HUD said it was reviewing its programs for making its foreclosed properties available to the homeless. Both lease and lease-purchase programs are available, and about 90 percent of HUD-owned houses can be purchased at a 10 percent discount by local agencies that would make them available to the homeless, HUD said.

Foreclosed government properties are generally available through bids that are to be opened on a specific date for each property. Before the program was stopped, HUD had asked its field offices to do everything they could to promote house sales this weekend, including offering incentives, holding open houses, and placing ads for the properties.