Americans enter the 1981 holiday season with gloomy expectations for themselves and increasingly critical views of Ronald Reagan's handling of the economy, according to a new Washington Post-ABC News poll.

The poll shows citizens reacting defensively to the state of the economy by curtailing purchases. Three in five say they will cut back spending for Christmas gifts this year; four in 10 say high interest rates have forced them to forgo purchases.

The findings show a steady erosion of support for Reagan's approach to the economy. In the new poll, conducted by telephone from Nov. 17 to Nov. 22, 49 percent of those interviewed say they disapprove of Reagan's handling of the economy, while 45 percent say they approve. A month earlier, a Post-ABC News poll showed 54 percent approval and 39 percent disapproval.

Similarly, the new poll shows sharp concern over growing unemployment and dissatisfaction with Reagan because of it. A total of 57 percent say they disapprove of Reagan's response to the issue of unemployment and 34 percent say they approve, percentages much less favorable to the president than those recorded up to now.

By a narrow plurality of 47 percent to 41 percent, Americans still feel that the Reagan tax and spending cuts that took effect Oct. 1 will help rather than hurt the economy in the days ahead. But even those figures represent a decline for the president. Until recently, there was more faith in those cuts, the heart of the Reagan program. And in February, when Reagan announced his proposals, citizens felt by more than a 2-to-1 majority that they "would help bring an end to inflation."

There is, in addition, apprehension over Reagan's request for still more spending cuts.

Question: "Reagan has proposed a 12 percent cut in spending in addition to the one that took effect on Oct. 1. What is your best guess--if spending is reduced by an additional 12 percent, will that mainly reduce waste in domestic programs, or will that mainly damage programs the country needs?"

Answer: By almost a 2-to-1 majority, 54 percent to 29 percent, citizens say the proposed new cuts would damage needed programs rather than eliminate waste.

The new poll continues to show a majority of the public holding the view that Reagan "cares more about serving upper-income people" than about serving any other income group or serving all people equally. Fifty-four percent say Reagan favors the rich; 1 percent say he cares more about the poor; 7 percent say he cares more about middle-income people; 35 percent say he cares equally about serving all people; and 3 percent express no opinion.

The poll suggests that one factor adding to the growing skepticism may be the recent magazine article in which Reagan's budget director, David A. Stockman, expressed doubts about the President's economic program.

Two-thirds of those interviewed said they had heard or read of the Atlantic Monthly magazine article.

Those who said they had heard or read of it were asked "whether the reports of the Stockman magazine article give you a more favorable or less favorable impression of Reagan's plans for the economy." The response was overwhelmingly negative: 54 percent said "less favorable," 7 percent said "more favorable," and 32 percent said the article made no difference in their views.

The poll shows the public in agreement with Reagan administration economists who say the nation is in a recession. Overall, 55 percent say the nation's economy is getting worse and only 11 percent say it is getting better. That is a sharply more pessimistic view than the public has held at any time since Reagan took office. In May, for example, 36 percent said the economy was getting worse. In October, according to a Washington Post-ABC News poll, the figure was at 40 percent.

One effect of the recession, according to the poll, will be somewhat less under the tree and in the stocking at Christmas time. Asked whether they will cut back on spending for gifts this year compared to last, 3 in every 5 interviewed say they will. For lower-income people the percentage who say they will spend less is higher, but almost half those with annual incomes of $50,000 or more also say they will cut back.

Four in 10 Americans say that they have had to forgo purchases this year because of high interest rates. Of that group, fully a third say they have been unable to buy or sell a house because of interest rates, and 40 percent say they had decided to buy a car but didn't because of interest rates. Translated roughly, that finding means that at least 8 million households had plans to buy an auto but were unable to.

Along with the decline in optimism about Reagan's economic program has come a drop in support for the president himself. The new poll shows 53 percent saying they approve of Reagan's handling of the presidency and 38 percent saying they disapprove, the lowest rating he has received in a Post-ABC News poll. Those figures are similar to the findings of a recent Gallup poll, in which it was noted that Reagan is held in almost exactly the same regard as was Jimmy Carter at the same point in his presidency.

The country appears much more polarized over Reagan than it was over Carter, however. In a pattern that developed during last year's presidential campaign, men continue to hold one view of the president and women quite another. Men give Reagan an overall rating of 60 percent favorable, 33 percent unfavorable; women are almost evenly divided at 47 percent favorable, 43 percent unfavorable.

Among blacks, who have expressed skepticism of Reagan from the outset, only 19 percent say they approve of his handling of the presidency--about the same as in the most recent Post-ABC News poll.

Perhaps the sharpest decline in support comes from Democrats. Early in his administration, Reagan had a high level of support from Democrats, but by summer it began to wane. In the new poll, only 31 percent of the Democrats give him a favorable rating, and 59 percent an unfavorable rating.