The Bush administration has cautioned against hopes of a quick breakthrough as it begins a new attempt to arrange an Israeli-Palestinian cease-fire and open the way to renewed peace talks.

The dispatch to the region of Assistant Secretary of State William Burns and retired Marine General Anthony Zinni is the most visible element of the administration initiative, launched a week ago by Secretary of State Colin Powell.

They hope to nail down Israeli and Palestinian compliance with a U.S. cease-fire plan negotiated last May, and to put the parties on a path back to peace negotiations, after more than a year of violence.

State Department spokesman Richard Boucher says it will not be an easy process. "I would not expect instant results," he said. "I would not expect their arrival in the region to suddenly and magically be greeted by a total cessation of the violence. They're going to work on this, and they're going to work very hard on it."

General Zinni, the former chief of U.S. forces in the Middle East, will have an open-ended series of cease-fire meetings with the parties, while Mr. Burns holds broader talks with leaders in the region.