Postpone the panda shower.

Once high hopes for the birth of a baby panda this year are fading at the national zoo, disappointed officials acknowledged yesterday.

The time in which Ling-Ling, the zoo's female giant panda, could be expected to give birth if she is pregnant is rapidly drawing to an end.

If nothing happens by early next week, zoo Director Theodore Reed said he will call off the 24-hour watch on Ling-Ling that started in mid-July, four months after she was artificially inseminated with sperm from two giant pandas, including her bunkmate, Hsing-Hsing.

The anticipated pregnancy has been a matter of watching and wondering all along because, zoo officials say, it is virtually impossible to determine whether a panda is pregnant until a birth occurs.

But by Monday, Ling-Ling would have reached the longest recorded panda gestation period of 163 days. Reed said it would be unlikely that she could be pregnant if she does not give birth by then.

Dr. Robert J. Hoage, Reed's special assistant, said there are a number of possible explanations for Ling-Ling's on-again-off-again signs of pregnancy.

"She was pregnant, or she still is pregnant," he said. "If she isn't pregnant, she could have miscarried in a fashion that we didn't notice, without leaving a trace of blood or fluid."

Another explanation: "It could have been a pseudo-pregnancy or false pregnancy." Only one problem: "That's never been known to happen in pandas," Hoage said.

As time and hope run out on the sixth annual attempt to produce a baby panda, a maybe-next-year attitude is setting in around the panda house and its staff.

One panda expert is taking her French champagne back home, convinced that the big event won't occur anytime soon. And the biggest wager on the possibility that Ling-Ling is indeed pregnant is reported to be 25 cents.

For some time the 239-pound Ling-Ling was displaying indications of possible pregnancy -- erratic eating habits, nest-building and general restlessness. Those signs peaked two weeks ago, and since then, officials say, her behavior has been returning to normal. "She's losing interest in it," Reed said yesterday.

Last month, the panda house was closed to the public to give the possibly pregnant panda the privacy any expectant mother would expect, zoo spokesmen explained at the time.

More than 100 "panda watch" volunteers and scientists began studying Ling-Ling 24 hours a day on television monitors set up in the panda house kitchen.

The volunteers will continue the watch at least until Monday, hoping against dwindling hope for the arrival of a four-ounce product of the possible pregnancy that would be the first panda born in the United States.