Amtrak president Paul H. Reistrup told his board of directors yesterday that the national rail passenger service will begin posting notices in rail stations this week detailing an uprecedented curtailment of services in the next fortnight.

But the effective date of the cut-backs will be delayed until Nov. 6 because of labor agreements requiring seven-day notices for work schedule changes. Amtrak earlier said the curtailments would take place next Sunday.

Reistrup's announcement came within hours of a House vote, Tuesday night, in favor of an appropriations bill that did not include extra money that Amtrak had requested for the new fiscal year.

Although Amtrak officials said yesterday they remain hopeful that Senate action still could add the new funds. Carter administration opposition may prove fatal to the drive for supplemental appropriations, congressional sources said.

Sen. Birch Bayh (D-Inl), chairman of the Senate Transportation Approriations Subcommittee, said he intends to offer an amendment that would add $18 million to Amtrak's operating subsidy for the current fiscal year, which started Oct. 1.

Amtrak originally asked for $534.1 million to cover operating losses in the fiscal year. President Carter asked for $500 million and Congress appropriated $488.5 million. Amtrak's board then voted to seek an additional $56.5 million, with the administration board member casting the lone negative vote.

To balance Amtrak's books, the first broad cutbacks in rail passenger service this decade were ordered and more are planned after Jan. 1.

Cutbakds planned for Nov. 6 will reduce spending bu $28 million and cost about 1,000 workers their jobs. Amtrak has estimated. An average of 22 trains a day out of 120 in the heavily traveled Boston-Washington corridor will be estimated. Two trains linking Union Station with the Midwest - the Hilltopper and Shenandoah - will be redured from daily to four-times-a-week operation.

Amtrak also announced a series of schedule changes and train speedups to take effect Sunday, which are not associated with the budget squeeze, but age tied to the end of Daylight Savings Time.

Because of improved track conditions and improved track conditions and repaired locomotive equipmeent in some sections of the country, 26 trains will have their travel timetables reduced. For example, the North Coast Hiawatha between Chicago and Seattle now will be scheduled to operate five hours faster than under current timetables.