Elisabeth Bumiller | David Sanger | NYTimes.com Defense Secretary Robert M. Gates, Adm. Mike Mullen, the chairman of the Joint Chiefs of Staff, and Secretary of State Hillary Rodham Clinton are coalescing around a proposal to send 30,000 or more additional American troops to Afghanistan, butPresident Obama remains unsatisfied with answers he has gotten about how vigorously the governments of Afghanistan and Pakistanwould help execute a new strategy, administration officials said.Mr. Obama is to consider four final options in a meeting with his national security team on Wednesday, his press secretary, Robert Gibbs, told reporters. The options outline different troop levels, other officials said, but they also assume different goals — including how much of Afghanistan the troops would seek to control — and different time frames and expectations for the training of Afghan security forces.Three of the options call for specific levels of additional troops. The low-end option would add 20,000 to 25,000 troops, a middle option calls for about 30,000, and another embraces Gen. Stanley A. McChrystal’s request for roughly 40,000 more troops. Administration officials said that a fourth option was added only in the past few days. They declined to identify any troop level attached to it.Mr. Gates, a Republican who served as President George W. Bush’s last defense secretary, and who commands considerable respect from the president, is expected to be pivotal in Mr. Obama’s decision. But administration officials cautioned that Mr. Obama had not yet made up his mind, and that other top advisers, among them Vice President Joseph R. Biden Jr. and the White House chief of staff, Rahm Emanuel, remained skeptical of the value of a buildup.In the Situation Room meetings and other sessions, some officials have expressed deep reservations about President Hamid Karzai, who emerged the victor of a disputed Afghan election. They said there was no evidence that Mr. Karzai would carry through on promises to crack down on corruption or the drug trade or that his government was capable of training enough reliable Afghan troops and police officers for Mr. Obama to describe a credible exit strategy.Officials said that although the president had no doubt about what large numbers of United States troops could achieve on their own in Afghanistan, he repeatedly asked questions during recent meetings on Afghanistan about whether a sizable American force might undercut the urgency of the preparations of the Afghan forces who are learning to stand up on their own.“He’s simply not convinced yet that you can do a lasting counterinsurgency strategy if there is no one to hand it off to,” one participant said.Mr. Obama, officials said, has expressed similar concerns about Pakistan’s willingness to attack Taliban leaders who are operating out of the Pakistani city of Quetta and commanding forces that are mounting attacks across the border in Afghanistan. While Pakistan has mounted military operations against some Taliban groups in recent weeks, one official noted, “it’s been focused on the Taliban who are targeting the Pakistani government, but not those who are running operations in Afghanistan.”Mr. Obama himself seems to be hedging his bets, particularly on the performance of Mr. Karzai, who is considered by American officials to be an unreliable partner and is now widely derided in the White House. Mr. Obama told ABC News during an interview on Monday that given the weakness of the Karzai government in Kabul, his administration was seeking “provincial government actors that have legitimacy in the right now.”Officials said that while Admiral Mullen and Mrs. Clinton were generally in sync with Mr. Gates in supporting an option of about 30,000 troops, there were variations in their positions and they were not working in lock step. Admiral Mullen’s spokesman, Capt. John Kirby, said that the admiral was providing his advice to the president in private and would not comment. Geoff Morrell, the Pentagon press secretary, would not comment on Mr. Gates’s position.A focus of Mr. Obama’s meeting on Wednesday with his national security advisers, officials said, will be to discuss some of their differences as well as those of the president’s other advisers. Officials also said there was a possibility that Mr. Obama might choose to phase in additional troops over time, with a schedule that depended on the timing of the arrival of any additional NATO troops and on how soon Afghan security forces would be able to do more on their own.Officials said that no decision was expected from Mr. Obama on Wednesday, but that he would mull over the discussions at the meeting during a trip to Asia that begins Thursday. Mr. Obama is not due back in Washington until next Thursday. Officials said that it was possible that he could announce his decision in the three days before Thanksgiving, which is on Nov. 26, but that an announcement in the first week of December seemed more likely.Should Mr. Obama choose to send about 30,000 troops, a military official said, brigades would most likely be sent from the 101st Airborne Division at Fort Campbell, Ky., and the 10th Mountain Division at Fort Drum, N.Y. In addition, 4,000 troops would be sent as trainers for the Afghan security forces, the military official said. A brigade is about 3,500 to 5,000 soldiers.Senator Jack Reed, the Rhode Island Democrat who has been an influential adviser in the Afghanistan debate, said that one of the most difficult issues was determining the effects of a large American troop presence on the country.“It’s more about, hey, are we creating such a large footprint that it’s easier for the Afghans to walk way from their responsibility?” Mr. Reed said. “I don’t think that’s one that can be resolved. You’re making a judgment about that one, and not one you can solve with arithmetic.”Peter Baker, Eric Schmitt and Mark Landler contributed reporting.