U.S. President-elect Barack Obama has repeated his pledge to close the Guantanamo Bay prison facility, but he says it may not happen within his first 100 days in office.

In an interview with U.S. television network ABC's This Week broadcast Sunday, Mr. Obama said closing the prison is more difficult than many people realize.  But he said his administration eventually will shut it down.

Mr. Obama also discussed the conflict in Gaza during the wide-ranging interview.  He said the deaths of Palestinian and Israeli civilians are "heartbreaking."

But he declined to speak at length about the conflict, repeating what he has said before - that the United States cannot have two administrations sending signals in a volatile situation.

In a separate interview, outgoing U.S. President George Bush looked back on his eight years in office, telling the Fox News Sunday program he is proud of his accomplishments. 

Mr. Bush is leaving office with low public approval ratings, and turns over a nation at war and in the midst of an economic crisis.

On the subject of Iran, Mr. Obama promised a new approach starting with engagement.  The president-elect said he believes Iran will be one of his administration's "biggest challenges," and that the international community likely will take its cues from the U.S. on how to approach Iran.