* Ban Ki-moon urges parties to stick to deal
* U.N. chief says tough talks to flesh out ceasefire
AMMAN Nov 21 (Reuters) - U.N. Secretary General Ban Ki-moon urged Israel and the Palestinian Hamas movement to stick to pledges under a ceasefire deal which came into effect on Wednesday to end the eight-day conflict around the Gaza Strip
"We urge the parties who agreed to the ceasefire to keep their promises. There may be still challenges in the course of implementing this agreement," Ban told reporters after talks with King Abdullah at the monarch's residence in the Jordanian capital.
Ban urged the two sides to exercise "maximum restraint and patience with mutual understanding".
"I commend the parties for stepping from the brink and commend President Mursi of Egypt for his exceptional leadership," Ban said.
"Our focus now must be on ensuring that the ceasefire holds and all those in need in Gaza and there are many receive the humanitarian assistance they need," he added.
Ban said tough talks lay ahead to iron out the ceasefire.
"I know the parties will sit down together and detail out implementing the provisions. It is still very hard but we are encouraged and we are relieved they have at last agreed to halt the fire. This is a very important historic moment."