WASHINGTON, April 30 (AFP) - UN top war crimes prosecutor Louise Arbour delivered a powerful call Friday for the arrest of indicted Bosnian Serb leaders saying it would be the best way to deter atrocities in Kosovo, as questions arose about her position.

Arbour hinted that the arrest and prosecution of Bosnian Serb leaders Radovan Karadzic and Ratko Mladic earlier might have prevented the horrific acts being described by ethnic Albanian Kosovars as they flee a Serbian ethnic cleansing campaign.

"The strongest deterrent message that could have been sent into Kosovo, and that could still be sent, would be the immediate apprehension, not only of the remaining indictees who are publicly indicted, but of the persons who are the subject of sealed indictments," Arbour said.

But the chief prosecutor for the International Criminal Tribunal for the former Yugoslavia (ICTY) in The Hague declined to comment on whether her office would indict Yugoslav President Slobodan Milosevic whom NATO leaders have accused of being politically responsible for the ongoing Kosovo war crimes.

Speaking at a joint press conference with US Secretary of State Madeleine Albright, Arbour said her talks with Albright had centered on the "need for an immediate, very robust arrest initiative in Bosnia."

Albright gave a broad affirmation of the US desire to help the tribunal as much as possible, both in Bosnia and Kosovo.

"More than half of those who have been publicly indicted have been arrested or are incarcerated in The Hague," Albright said. As for Karadzic and Mladic, she said, "Their day will come."

Arbour has expressed frustration at the delay in arresting Bosnian war criminals in nearly every capital she has visited and appeared to be using recent reports of atrocities in Kosovo to underscore their importance.

"I believe that this would bring an air of reality to those who are in positions of accountability in Kosovo who may be associated with the perpetration of the crimes that, by credible accounts, appear to be being committed now," she said.

Arbour, in the United States for meeting with US and UN officials on a variety of tribunal-related topics, including funding and the funneling of more information on Kosovo war crimes to her office, sidestepped questions about her own future.

She refused to comment on reports she would be stepping down from the chief prosecutors' post.

"I don't think it's appropriate for me to speculate on hypothetical circumstances such as this one," she said, referring to a New York Times report that said Arbour, as a top candidate for Canada's Supreme Court, planned to leave the tribunal.

"I think others will have to make some decisions ... but I don't think it's appropriate for me to speculate."

The Times said US officials were concerned that Arbour's departure might seriously hamper the work of the tribunal at a time when it is actively pushing to have it investigate Kosovo atrocities.

At the same time, some US officials told the paper they were concerned that Arbour had not been forceful enough at her job but were afraid they might not be able to find a better candidate if she left.