The White House is urging all parties in the Middle East to exercise restraint. The appeal comes hours after a bomb killed six Palestinians in a dawn explosion and both Israelis and Palestinians exchanged rocket and mortar fire in Gaza, killing and injuring others.

"The United States urges restraint on all parties and urges all parties to do their level best to achieve a lasting cease-fire," said spokesman Ari Fleischer.

During a session with reporters, Mr. Fleischer was asked about prospects for sending international monitors to the region. He said that can not even be considered until a cease-fire is firmly in place.

"Specifically, and only at that time will the question of monitors possibly come up, and in that context, the president has said that on the topic of monitors it would have to be agreed to by both sides," he said.

The Palestinians favor observers, but Israel is opposed to international monitoring.