Members of Washington's hotel and restaurant workers union yesterday authorized their leaders to call a strike against hotels here if a new contract agreement is not reached when the old contract expires at midnight Friday.

Waiters, waitresses and maids who belong to Local 25 of the Hotel and Restaurant Workers Union voted the authorization by 778 to 6 in a meeting at the Shiloh Baptist Church, 9th and P Streets NW.

Negotiators for both the union and the 39 hotels represented by the Hotel Association appeared gloomy about prospects for averting a walkout, which would be the first of its kind since 1946.

The union is demanding a $20-a-week pay increase in each year of a three-year contract, while the association has offered $3 a week every six months and is proposing a four-year contract, according to Ron Richardson, union secretary-treasurer.

He put the likelihood of a strike by the union's 6,000 members of "90 percent," asserting that bargainers are "far apart on everything."

Allen G. Siegel, chief negotiator for the Hotel association, would give no details of the bargaining but said that there have been "a great deal of problems in resolving every issue because of the union's intransigence."

Other issues said to be involved in the bargaining are union demands for no compulsory overtime, free meals for all hotel workers and increased seniority for shop stewards, Richardson said.