American Telephone & Telegraph Co., five days into its nationwide strike by 155,000 union members, yesterday announced plans to hire more than 7,000 temporary replacements, and sent letters to strikers outlining the company's final contract offer, which the union rejected on Saturday.

As the strike neared the end of its first business week, AT&T said it had improved its ability to handle a daily volume of about 3 million operator-assisted long-distance calls. The company is using supervisors on 12-hour shifts and about 3,000 temporary replacements -- with 4,000 more to be hired shortly -- to fill in for 38,000 operators on strike.

The striking Communications Workers of America, which has asserted that AT&T stands to lose $60 million a day in revenues, said that while the company has improved service, it is still losing millions of dollars a day because of the diminished volume of operator-assisted calls, the most profitable chunk of the AT&T network. AT&T is also losing income because of a sharp drop in installation of new telecommunications and computer equipment.

AT&T said callers making collect, person-to-person or emergency calls are now encountering average delays of about 14 seconds, compared with 30 seconds earlier this week. The normal time is 2.1 seconds.

No significant progress was reported in the intermittent talks under way here between AT&T executives and leaders of the 600,000-member union. Both sides were girding for a prolonged strike, with the company also planning to hire temporary technicians, and the union readying strike-benefit plans to help support strikers' families.

AT&T spokesman Herb Linnen said the company is hiring temporaries through employment agencies and through recruitment of AT&T retirees, but plans to offer jobs to all strikers once the strike ends.

In letters sent to the residences of strikers and in newspaper advertisements today, AT&T outlined the terms of what it called "A Fair Offer to the Best People in the Business." That offer has been tentatively accepted by its smaller union, the International Brotherhood of Electrical Workers, which represents 41,000 AT&T workers.

"Their letters and advertising indicate they really want their work force back, and we just wish they would show the same resolve at the bargaining table," CWA spokeswoman Rozanne Weissman said.

The three-year contract would provide pay raises of 2 percent this year and 3 percent in each of the next two years.