After months of hesitancy, leading Democrats have begun to challenge President Bush directly on his conduct of foreign affairs, offering pointed criticisms of his policies on the Middle East, U.S. relations with key allies and even the war in Afghanistan.

The new posture represents a sharp departure from the "shoulder-to-shoulder" rhetoric that emerged in the immediate aftermath of Sept. 11. Fueling it are concerns about the direction of U.S. policy, growing confidence that the public will tolerate vigorous debate and early jockeying among prospective 2004 presidential candidates.

At a time when some party strategists have urged candidates to focus on domestic issues as the November elections near, a number of Democrats fear the open-ended nature of the war on terrorism will put the party at a long-term disadvantage if they cede discussion about foreign policy to the White House.

The emerging critique underscores the lessons learned by Democrats more than a decade ago, when the Vietnam hangover inhibited most party leaders from advocating an interventionist foreign policy and caused majorities of Democrats in the House and Senate to oppose the resolution authorizing the Gulf War. Democrats have urged Bush to do more, not less.

"We're still shoulder to shoulder on the war itself," said Sen. John F. Kerry (D-Mass.). "There's no dissension about whether we have to win. The difference is whether we're doing the things necessary to do that."

Kerry has been the most aggressive and comprehensive in his criticism of the administration, using a recent appearance on NBC's "Meet the Press" to accuse the administration of making a "catastrophic mistake" with its initial Middle East policy. He described the battle of Tora Bora in Afghanistan as "a failed military operation" and the subsequent Operation Anaconda as one "which also did not do the job."

In a recent telephone interview, Kerry offered an across-the-board critique of the administration's foreign policy.

"It's reluctant. It's shifting. It's inconsistent -- and to some measure disengaged globally," he said. "It's reactive, not proactive. Up until 9/11 it was singularly unilateral. Since then it's less so, but not half as forceful and encompassing as I think America's foreign policy ought to be at this moment. Not as bold and not as visionary."

Other prospective presidential candidates also have raised questions about the administration's foreign policy or homeland security. They include: Why do Osama bin Laden and other al Qaeda leaders remain at large? Was the president's recent speech on the Middle East a pretext for disengagement, and is the United States doing enough to bring stability to Afghanistan or to protect the homeland from attacks?

On Iraq, however, there is no clear consensus among Democrats, beyond agreement that Iraqi President Saddam Hussein is a menace.

Democrats have stepped up their criticisms mindful that Bush retains strong support for the war on terrorism. Indeed, some analysts question whether the charges leveled by Kerry, former vice president Al Gore and Senate Majority Leader Thomas A. Daschle (D-S.D.) about the failure to capture bin Laden and other terrorist leaders can be sustained politically.

"My own view is that criticizing the conduct of the war against al Qaeda is a mistake, whether it is deserved or not," said a former government official. "I just don't think the public really wants that debated. I think the larger issues of America's role in the world and the extent to which we are isolating ourselves as opposed to isolating the bad guys is a legitimate issue, but it's got to be taken away from the war on terrorism and made in broader terms."

A former Clinton administration official agreed that there is still a "protected zone around the president at a time of war." But the official also said many new issues have been put on the table since Sept. 11 that "are not as black and white as they were with respect to a direct attack on the country" and deserve a thoughtful critique from an opposition party.

Sen. John Edwards (D-N.C.) and Gore have sharply questioned the administration's commitment to nation-building in Afghanistan. Gore charged recently that Bush's policies threaten to bring a return to chaos and control by regional Afghan commanders.

On the Middle East, Democrats have criticized the administration's initial decision to disengage from the region, and some said Bush's most recent speech, in which he called for Palestinians to replace Yasser Arafat and others in the leadership, set out conditions that would be so difficult as to be impractical. But they have been reluctant to offer public pressure on Israel to alter any of its tactics, either in combating terrorist attacks or halting settlement activity.

Beyond that, Democrats have challenged the administration's tendency toward unilateralism in its approach to foreign policy.

"One of the things the Bush campaign said was it was going to carry itself humbly in the world," said Leon Fuerth, who was national security adviser to Gore when he was vice president. "But if anything, the administration has shocked the rest of the world because of its disregard for the opinions of the rest of the world, its sense that trusted alliances have become irrelevant, its projection of the idea that the United States can go it alone and will go it alone unilaterally."

The longer the war has continued and the more Bush has made it the centerpiece of his administration, the more restive Democrats have become. "The open-endedness of the situation is settling in on people," said a former Clinton administration official. "It's not as if you could wait until the end of the 'war' before you resume the normal give-and-take of political life. The question has to be faced: 'If not now, when?' "

The prospective Democratic candidates have watched one another test the environment and have measured the response, from both the administration and the public. Last winter, when Daschle offered mild criticism of the administration, he was met by a fierce Republican counterattack that questioned his patriotism. The most recent criticisms from Kerry and Gore drew a response from administration officials, but not a challenge to their patriotism.

Kerry finally went public with his complaints about the war strategy after months of frustration with what he was seeing. One Kerry adviser said the senator's criticism grew out of his belief that U.S. ground forces in Afghanistan were not being well served by administration officials. "At some point, being the loyal opposition requires some vocal dissent and well-thought-out criticism, where merited," the adviser said.

Kerry, a decorated Vietnam War veteran who came back to the United States to become a leader in the anti-war movement, said his experiences in that conflict shaped his views about the importance of challenging the administration.

"One of the great lessons I learned in Vietnam the hard way is that bad things happen when people don't ask hard questions," he said.

He was quick to describe Bush's most recent Middle East speech as "only half a loaf" and jousted last week with Secretary of State Colin L. Powell over the new nuclear arms treaty with Russia.

Kerry said he continues to have deep reservations about the war on terrorism but remains reluctant to outline his views in detail.

"If I really lay it out there, it's going to be a major criticism because I really differ with the way they began the war," he said. "I think it was not effectively targeted with respect to al Qaeda and Osama bin Laden from almost Day One. I'm not going to go into now what I would have done differently but . . . it begins at the beginning. Strategic and covert activities could have been far more effective."

Iraq presents a difficult issue for the Democrats. Some argue that the administration needs to make a more effective case to rally support internationally before taking any serious action to oust Hussein, but they are reluctant to take on Bush directly. Among prospective 2004 candidates, Sen. Joseph I. Lieberman (D-Conn.) and House Minority Leader Richard A. Gephardt (D-Mo.) have expressed the strongest support for military action, if necessary, to oust Hussein.

"The dilemma the Democrats face is [that] nobody particularly wants to be on the wrong side of the Gulf War vote of 1991, and yet I think there is uneasiness about the circumstances under which this would be done," said a former government official, who asked not to be identified.

As Democrats wade into these and other foreign policy issues, the debate with the administration is likely to broaden. Fuerth said the party should not shrink from raising questions about Bush's policies.

"What you have to look at is whether the Republicans have got a model of where the world should end up and an idea about how to get there, and if they've got these things, how well are they doing in moving the country and the rest of the world in that direction," he said.

Sen. John F. Kerry (D-Mass.) has accused the White House of making a "catastrophic mistake" with its initial policy on the Middle East.