President Bush and Prime Minister Tony Blair are going to work with their new partners in Iraq to determine when the Iraqis can sustain themselves and coalition forces can drawdown, the president said in a press conference with Blair on Thursday night.

"I have said that our commanders on the ground will make that decision. I will talk to General Casey once he has conferred with the new government in Iraq. They are in the process of getting a defense minister, they don't have a defense minister yet ... it probably makes a lot of sense for our commander on the ground to wait until their defense structure is set up before we discuss with them and he with me the force levels necessary to reach our objective," Bush said.

Blair came away from his visit to Iraq speaking very positively and optimistically about its new government and new Prime Minister Nouri al-Maliki. He said "it is the duty of the whole international community" to confront the forces that are trying to destroy the hopes of Iraqis who want to live the same type of life as those in free and democratic nations.

"I'm more than ever convinced that what is important for them in Iraq is to know that we will stand with them in defeating these forces of reaction," Blair said.

"I came away thinking that the challenge is still immense, but I also came away more certain than ever that we should rise to it. And though it is at times daunting, it is also utterly inspiring to see people from all the different parts of the community in Iraq — the Sunni, the Shia, the Kurds — sitting down together, all of them democratic leaders, democratically elected by their people, elected for a four-year term, elected and choosing to come together as a government of national unity, and completely determined to run their country in a different way for the future," he said.

Blair arrived at the White House just before 6:30 p.m. EDT, where he met privately with Bush to debrief the president on the trip, the new government and his face-to-face meetings with Maliki.

When Blair was in Iraq, one of his aides was quoted as saying coalition forces would be reduced to below 100,000 by the end of this year, and would be taken out of Iraq completely in four years.

Bush said that 100,000 threshold is one tossed around, but holds no meaning to him.

"That's some speculation in the press that they haven't talked to me about," Bush said of his defense team.

The United States has about 131,000 troops in Iraq; officials have said they would like to have about 100,000 by year's end. Britain has about 8,000. At least 2,460 members of the U.S. military have died since the beginning of the war. Britain has lost 106 service personnel.

"I want our troops out, don't get me wrong. ... I fully understand the pressures placed on the military and our families, but I also understand that it is vital that we do the job, that we complete the mission," Bush said, noting that the "unconventional enemy" could pervade around the world.

Gen. Peter Schoomaker, the Army chief of staff, said his service, which supplies about 105,000 to 110,000 soldiers to Iraq, is planning for the possibility of having to maintain current troop levels in Iraq for the next two years, while also anticipating the possibility of cuts.

"We're continuing to plan for a variety of troop levels," he said. "Obviously we're planning to be able to sustain the levels that we have today, but we're running alternatives as well, in anticipation that we'll be asked to do some different levels."

Maliki is being described as a decisive, action-orientated leader. On Thursday, he said Iraqi security can assume control by the end of next year. A senior administration official said it's great that Maliki is setting aggressive goals and milestones for achievement, and the coalition must help.

Though U.S. officials are not predicting schedules, Iraq's Vice President Tareq al-Hashemi said Thursday that Blair was urged to discuss them during his trip to Baghdad.

"We have discussed this thoroughly and I convinced him of the necessity of announcing a timetable for the withdrawal of the occupying troops and told him frankly that Iraqis have a right to know when the last British or American soldier will leave Iraq," al-Hashemi said.

Blair said that Iraq's leaders meant that it would be dependent on conditions on the ground. The goal is to have Iraqi security forces "take control progressively of their own country."

"For that to happen, the first thing obviously we need is a strong government in Baghdad" prepared to enforce its rule throughout the country," Blair said.

White House officials said before the press event that they hoped it would provide an opportunity for the American people will see that Iraq is now a committed and effective partner and the United States and Great Britain must stand with them.

White House aides said much of the meeting between the two leaders was about finding ways for the United States and the United Kingdom to help Iraq's new government succeed.

Some have speculated that the press briefing was designed to bolster the two leaders' popularity — the president's popularity polls are in the 30s, Blair's are even lower in the 20s. The White House and Downing Street say those suggestions are nonsense and insist the formation of Iraq's new government is a hugely important development that cannot be highlighted enough.

"All of our efforts over the past three years have been aimed toward this goal. And this past weekend, the world watched as Iraqis stood up a free and democratic government in the heart of the Middle East," Bush said.

Blair said the progress in Iraq has nothing to do with Bush and Blair's hopes for better poll numbers.

"I don't really think it's a matter of our vindication. I think in a way that's the least important part of it," he said.

"A large part of the perspective with which we look at this is to see every act of terrorism in Iraq, every piece of ghastly carnage on our television screens, every tragic loss of our own forces. We see that as a setback and as a failure, when we should be seeing that as a renewed urgency for us to rise to the challenge of defeating these people who are committing this carnage. ... These people who are fighting there know what is at stake, the question is: Do we?" Blair said.

Blair's approval ratings at home were reflected last week when local elections placed his Labour Party third in the polls, with 26 percent of the national vote and nearly 300 fewer council seats.

The results will have the impact of accelerating Blair's departure. Though the Conservative Party is now dominant in local British government, and would seem a more natural ally to the U.S. president, Bush said he would miss Blair if he were gone.

"My attitude is I want him to be here so long as I am the president," Bush said. "I'll say one thing. He can answer the question. Don't count him out; let me tell it to you that way."

"Well, what more can I say?" Blair joked.

The president is in office until January 2009. Asked about his missteps, Bush said his vernacular has been a major one.

"Saying, 'Bring it on'; kind of tough talk, you know, that sent the wrong signal to people. I learned some lessons about expressing myself maybe in a little more sophisticated manner, you know. 'Wanted, dead or alive'; that kind of talk. I think in certain parts of the world it was misinterpreted. And so I learned from that," he said.

He also said the biggest mistake of U.S. involvement in Iraq were the events at Abu Ghraib prison in Iraq, where photographs of prisoners being mistreated and humiliated by American prison guards were shown around the world.

"I think that probably in retrospect, though at the time it was very difficult to argue this, we could have done de-Baathification in a more differentiated way than we did," Blair said in reference to the wholesale removal from power of Saddam Hussein's party loyalists.

Prior to the conference, the two leaders were to discuss the showdown with Iran over its suspected nuclear-weapons program and fading Mideast peace prospects. Afterward, neither would reveal their thinking on a possible package of incentives to draw Iran back to negotiations over its suspected nuclear-weapons program.

"One of the goals Tony and I have was to convince others in the world that Iran having a nuclear weapon would be very dangerous," Bush said, adding that they strategized about how to convince international partners that the United Nations is still the best bet right now to win compliance.

"Of course we'll look at all options but it's [Iran's] choice right now. They are the ones who walked away from the table," Bush said. Bush added that he read the letter Iranian President Mahmoud Ahmadinejad sent to Bush earlier this month, and noted that Ahmadinejad skipped the most important issue — Tehran's nuclear weapons pursuit.

"He didn't address the issues of whether or not they're going to continue to press for a nuclear weapon. That's the issue at hand," the president said.

The decision to hold the press conference at such an odd time of day, during dinnertime on the East Coast and rush hours everywhere else, was Blair's decision, say aides. The conference will be occurring in the middle of the night British time, but that's just a reality of time zones, say aides, who note that Bush's news conferences overseas frequently occur in the middle of the night U.S. time.

FOX News' Carl Cameron and The Associated Press contributed to this report.