Hundreds of patriotic residents have flooded blood-donor sites in the Washington area in response to the Persian Gulf War, but the American Red Cross said yesterday there is no blood emergency and it gently urged that people slow down.

Because blood has a shelf life of only 42 days and the U.S. military wants blood less than five days old, Red Cross officials said they do not want extra supplies unless American casualties begin to rise.

They said the rush to donate probably was spurred by a public service announcement on Alexandria radio station WCXR that there was an "urgent" need for donated blood because of the war. The announcement was meant to promote a long-planned blood drive sponsored by the Marriott Corp.

At the request of the Red Cross, the radio announcement was changed yesterday to say there was an "ongoing need" for blood, said WCXR promotion director Mark Lepidus. The announcement, however, refers to the Desert Storm campaign.

Although the Red Cross has made no special appeal for donors, many have shown up at the organization's Washington headquarters or have stood in line at sites where drives are regularly held, said spokeswoman Kathy Szymanski.

"On Monday, people waited for two hours to give blood at our headquarters," she said. "It was very appropriate they used their holiday to donate blood. We did not turn people away, but we did suggest they come back another time when they could schedule an appointment."

The surge in interest put the Red Cross in a ticklish position. It wants to maintain its daily level of 1,500 pints in storage in this area, but doesn't want to exceed it until there is a greater need.

The Red Cross said it is asking those who already have scheduled appointments in the next month to keep the date and not rush in this week.

"We are hoping for a planned, phased donation," said Vicki Thomas, associate director of donor services for the Washington area. "This is not an urgent or critical situation."

Meanwhile, Congress launched a blood drive of its own on Capitol Hill yesterday, as the House's freshman class urged Americans across the country to give blood. Among those supporting the effort were Rep. James P. Moran Jr. (D-Va.) and Del. Eleanor Holmes Norton (D-D.C.).

Although Red Cross officials were on hand, they said again that blood supplies in the area are adequate.