TOLEDO, Ohio (AP) _ Thousands of people caught a long-awaited glimpse of two giant pandas that went on display at the Toledo Zoo over the objections of a conservation group that wants the endangered animals returned to China.

The exhibit, which began Tuesday after nine months of planning, marks the first time the Chinese have permitted two pandas to be exhibited together at a U.S. zoo. The animals are on loan to the zoo until Aug. 21.

Le Le and Nan Nan made their debut before an invitation-only crowd of about 250. Later, the zoo opened its gates to hundreds who had waited in line since dawn.

About 5,000 people visited the zoo on Tuesday, zoo spokeswoman Betsy Clark said. The zoo has between 2,000 and 3,000 visitors on an average weekday. Up to 1 million are expected to see the pandas by the time the display ends.

''They're so cute,'' said Lorraine Grove, 18, of Port Clinton. ''I waited on line for three hours, but it was definitely worth it.''

The international World Wildlife Fund contends the exhibit could endanger the pandas and had gone to court to prevent the animals from going on display.

In Washington, the wildlife fund asked a federal court Tuesday to shut down the exhibit, charging it represents commercial use of the pandas in violation of the Endangered Species Act and an international wildlife convention.

The group asked for an expedited hearing, which is expected to be set after the U.S. Fish and Wildlife Service files its response within five days.

''It is the first short-term panda exhibit in which both animals are of prime breeding age and were taken from a captive breeding and research facility,'' said Kenneth Cook, spokesman for the wildlife fund.

''It is no exaggeration to say that among zoo professionals and conservationists, these might be considered to be among two of the most valuable animals on the planet.''

The zoo has spent nearly $3 million in preparing to exhibit the pandas, including $1.9 million for their quarters. Edwin Bergsmark, president of the Toledo Zoological Society, said the exhibit is aimed primarily at children.

''They are, perhaps, the last generation that will be able to enjoy seeing the giant pandas if the immense conservation efforts being employed by the Chinese do not receive unified support from the conservation world,'' he said.

Viki Billis and her 21-month-old son, Andrew, were among the first in line.

''This is very exciting for Toledo. We needed this. Every mother and father should take time out and bring their children to the zoo,'' Mrs. Billis said.