Three years after declaring major military operations over in Iraq, President Bush said Monday that a report from his two top foreign policy officials on their visit to Baghdad shows that Iraq's leadership is "more determined than ever to succeed."

"We believe we've got partners to help the Iraqi people realize their dreams," Bush said outside the Oval Office after meeting with Secretary of State Condoleezza Rice and Defense Secretary Donald H. Rumsfeld. "They need to know that we stand with them."

But Bush said that Rice and Rumsfeld didn't come back from their surprise joint visit to Iraq last week — intended to boost the standing and spirits of the newly formed permanent government in Baghdad — with all good news.

"There's going to be more tough days ahead," the president said, with Rice and Rumsfeld at his side. "It's a government that understands they've got serious challenges ahead of them."

Though Bush was emphasizing the positive, it was a decidedly less positive message than the one he offered from aboard an aircraft carrier, the USS Lincoln, on May 1, 2003. "The tyrant has fallen and Iraq is free," he said then, standing underneath a banner proclaiming: "Mission Accomplished."

Also Monday, the senior Democrat on the Senate Foreign Relations Committee proposed that Iraq be divided into three separate regions — Kurdish, Shiite and Sunni — with a central government in Baghdad.

In a speech in Philadelphia, Sen. Joseph Biden of Delaware suggested that a residual force would be left in place that would number about 20,000 — a force that presumably would prevent Al Qaeda and jihadists "from essentially taking Afghanistan and moving it to the nether regions of Iraq."

The White House rejected the idea of a partitioned Iraq, saying the Bush administration supports a "federal, democratic, pluralist and unified" country. "A partition government with regional security forces and a weak central government, as you are referencing, is something that no Iraqi leader has proposed and that the Iraqi people have not supported," White House press secretary Scott McClellan said.

On Sunday, the White House defended its prewar planning against criticism from an unlikely source — former Secretary of State Colin Powell.

In an interview broadcast Sunday in London, Powell revisited the question of whether the U.S. had a large enough force to oust Saddam Hussein and then secure the peace.

Powell said he advised now-retired Gen. Tommy Franks, who developed and executed the 2003 Iraq invasion plan, and Rumsfeld "before the president that I was not sure we had enough troops. The case was made, it was listened to, it was considered. ... A judgment was made by those responsible that the troop strength was adequate."

Rice, who was Bush's national security adviser at the time of the invasion, responded, "I don't remember specifically what Secretary Powell may be referring to, but I'm quite certain that there were lots of discussions about how best to fulfill the mission that we went into Iraq.

"And I have no doubt that all of this was taken into consideration. But that when it came down to it, the president listens to his military advisers who were to execute the plan," she told CNN's "Late Edition."

Rice said Bush "listened to the advice of his advisers and ultimately, he listened to the advice of his commanders, the people who actually had to execute the war plan. And he listened to them several times," she told ABC's "This Week."

"When the war plan was put together, it was put together, also, with consideration of what would happen after Saddam Hussein was actually overthrown," Rice said.

Powell was chairman of the Joint Chiefs of Staff during the 1991 Gulf War and is known for his belief in deploying decisive force with a clear exit strategy in any conflict.

"The president's military advisers felt that the size of the force was adequate; they may still feel that years later. Some of us don't. I don't," Powell said. "In my perspective, I would have preferred more troops, but you know, this conflict is not over."

"At the time, the president was listening to those who were supposed to be providing him with military advice," Powell said. "They were anticipating a different kind of immediate aftermath of the fall of Baghdad; it turned out to be not exactly as they had anticipated."

Rumsfeld has rejected criticism that he sent too few U.S. troops to Iraq, saying that Franks and generals who oversaw the campaign's planning had determined the overall number of troops, and that he and Bush agreed with them. The recommendation of senior military commanders at the time was about 145,000 troops.