WICHITA, Kan. (AP) _ A federal judge today ordered U.S. marshals to keep protesters from blocking the entrance to an abortion clinic after more than two weeks of demonstrations that have resulted in more than 1,000 arrests.

One marshal was on the scene this morning, but more were expected.

U.S. District Judge Patrick F. Kelly sent letters to Mayor Bob Knight, Police Chief Rick Stone and the U.S. Marshals Service saying that despite Knight's assurances Friday, Dr. George Tiller's clinic gate was blocked again this morning by protesters.

Knight opposes abortion. Last week, he and the city manager issued a directive to police that prohibited them from stopping people before they block the gate and ordered them to make arrests using the minimum amount of force necessary.

But today, the police chief said he has ordered his officers to prevent people from standing or sitting in front of the clinic gate. ''The federal marshals have requested our assistance in keeping the clinic open. We are assisting them,'' Stone said.

Tiller's lawyers obtained a preliminary injunction from Kelly on July 23.

Denis Amico, supervisor of the Wichita office of the U.S. Marshals Service, refused to say how many federal officers would be sent.

''The judge's court order will be enforced. The gates to the clinic will stay open,'' Amico said.

Ann Baker, who tracks the abortion protest movement from her 80 Percent Majority Campaign office in New Jersey, said federal officers have been used before to serve injunctions against abortion protesters - but never to enforce one.

Police arrested 94 protesters today on loitering charges, said police Lt. Jack Arnold. The more than 1,000 arrests in the two weeks of demonstrations have all been for loitering.

The clinic opened about 10 a.m., shortly after police carried away the last protester.

Operation Rescue, the national anti-abortion group, is sponsoring protests at three Wichita abortion clinics. Only Tiller's clinic is affected by the judge's order.

Operation Rescue's founder, Randall Terry of Binghamton, N.Y., remained jailed today after being found in contempt of Kelly's court order.

Tensions increased Sunday when hundreds of supporters of Operation Rescue gathered at a Wichita park. Protest leaders urged the crowd to join a new wave of protests beginning today.

''We're going to hang on a lot longer than a week or two,'' leader Keith Tucci told the crowd.

In a telephone call from jail, Terry urged the crowd to ''do what God tells you to do, and we will drive child-killers out of Wichita.''

Peggy Jarman, a spokeswoman for Tiller's Women's Health Care Services clinic and for the Pro-Choice Action League, said the federal agents were welcome.

''It's obvious that the people in power in this city are not going to take the actions that are necessary to control these people,'' Ms. Jarman said. ''I'm hopeful that the federal agents will take any and all actions that will make the clinics accessible for patients.''