CARLISLE, Pa. (Reuters) - President Bush tried to convince Americans on Monday he has a workable plan for Iraq as the United States and Britain asked the United Nations for a resolution endorsing the handover of power to an interim Iraqi government.

In a half-hour televised speech at the U.S. Army War College here, Bush sought to persuade Americans that he can turn around the deteriorating situation in Iraq, with just five weeks to go before the United States plans to hand over power to a caretaker Iraqi government on June 30.

He offered no major change of course in Iraq and no timetable for a U.S. troop withdrawal, but spoke of progress being made while predicting violence could get worse in the short run.

"As the Iraqi people move closer to governing themselves, the terrorists are likely to become more active and more brutal. There are difficult days ahead and the way forward may sometimes appear chaotic," said Bush, whose job approval rating has fallen to the lowest level of his presidency, suggesting he faces the possibility of defeat in the Nov. 2 election.

As he spoke, word came from a senior defense official that the Pentagon is considering replacing Army Lt. Gen. Ricardo Sanchez as the top military officer in Iraq.

However the official denied that the scandal over the abuse of Iraqi inmates by American soldiers at the infamous Abu Ghraib prison was the reason. "Him leaving Iraq has nothing to do with Abu Ghraib. His time is coming up," the senior defense official told Reuters.

Spreading violence and the scandal over the inhumane treatment of the prisoners by the U.S. military have pushed Bush's approval ratings to new lows five months before the Nov. 2 presidential election.

To try to repair the battered American image in Iraq, Bush said the United States would tear down Abu Ghraib with Iraqi approval after building a modern, maximum security prison.

Demolishing the prison would be a "fitting symbol of Iraq's new beginning," said a somber sounding Bush, who stumbled over the pronunciation of Abu Ghraib.

As evidence that the structure of a new Iraqi government is in place, Bush said U.N. envoy Lakhdar Brahimi will provide names this week of leaders of the interim Iraqi government.

He said Iraqis will have full sovereignty, but was not clear on how the new government will function in an atmosphere where insurgents seem to operate at will and recently killed a top political leader with a car bomb.

Bush said U.S. troops will remain in Iraq after the June 30 handover and troop levels will remain at the current 138,000 for as long as necessary. More will be sent if needed.

They will operate under U.S. command as part of a multinational force. The new force is to be authorized by a U.N. Security Council resolution circulated on Monday and is intended to give the new government an international stamp of approval.

The resolution, co-sponsored by Britain and distributed to U.N. Security Council members, would support the formation of a "sovereign interim government" to take office by June 30. It says that government would "assume the responsibility and authority for governing a sovereign Iraq."

Bush, who went to war in Iraq over weapons of mass destruction that have never been found, did not acknowledge making mistakes, but conceded some things had not gone according to plan.

He said one of the "unintended" consequences of Baghdad's swift fall more than a year ago was that "elite guards shed their uniforms and melted into the civilian population" only to reorganize, re-arm and adopted "sophisticated terrorist tactics."

With little more than a month to go until the handover, many in Congress believe the administration has raised more questions than it has answered about how long American forces will remain, what the costs will be, and when Iraqi security forces will be ready to take over from U.S. troops.

"What's most important now is to turn these words into action by offering presidential leadership to the nation and to the world," said John Kerry, Bush's Democratic rival for the White House.

"That's going to require the president to genuinely reach out to our allies so the United States doesn't have to continue to go it alone and to create the stability necessary to allow the people of Iraq to move forward."

With the rising turmoil in Iraq, Bush's approval rating has slumped. A poll by CBS News said 41 percent of those surveyed approved of the job Bush is doing as president, while 52 percent disapprove. Two weeks ago in the same poll, 44 percent approved. A year ago, two-thirds did.