Senior Afghan officials, alarmed by the Obama administration’s reappraisal of its Afghanistan strategy, said an increased U.S. military commitment is needed to roll back an emboldened insurgency.

They also cautioned about what they said would be dire consequences of any U.S. attempts to edge out President Hamid Karzai. Results from a presidential election last month gave Mr. Karzai a majority, but allegations of widespread ballot-stuffing have stalled the confirmation of his victory and undermined his credibility in the eyes of many Afghans.

These admonishments come after the top U.S. and allied commander in Afghanistan, Gen. Stanley McChrystal, warned that the war here may become unwinnable unless troop levels are raised and the momentum of insurgents is reversed in the next 12 months.

The Obama administration has yet to endorse these findings, and has called for a review of the U.S.-led war effort before making a decision on troop levels. Vice President Joe Biden in particular has expressed skepticism about the proposed troop increase. Senior administration officials said the review was necessary because the war plan that President Barack Obama announced in March was based on the assumption that the election would give Mr. Karzai new legitimacy.

As the war in Afghanistan becomes increasingly unpopular in the U.S. and Europe, one policy option under review in Washington advocates reducing ground forces and relying instead on surgical airstrikes against Taliban and al Qaeda targets on both sides of the Afghanistan-Pakistan border.

This would be a recipe for failure, warned one of Mr. Karzai’s senior associates, Education Minister Farooq Wardak. “Airstrikes alone cannot be a strategy to defeat the insurgency and the Taliban. If the air attacks are not followed up by ground operations, they do not yield the results one expects,” he said. “We need additional troops — but not forever.” According to Mr. Wardak, it will take five years before the Afghan army and police can fight mostly on their own.

Parliament member Mohammed Mohaqeq, a powerful former warlord representing the Hazara ethnic minority who backed Mr. Karzai’s re-election bid, offered a similar assessment.

“The current number of soldiers is not enough to defeat the Taliban,” Mr. Mohaqeq said. Should the U.S. start reducing its forces in Afghanistan — currently over 60,000 — “the country will go back to civil war,” he added. “The Taliban are capable of recapturing the capital and the government.”

Mr. Karzai’s spokesman welcomed Gen. McChrystal’s report and said he had no comment on the Obama administration’s review of policy options.

The Taliban’s recent advances to previously secure areas of northern and western Afghanistan were made possible, in part, by growing public anger over the incompetence and graft in Mr. Karzai’s administration, many analysts say.

This anger was reinforced by reports of large-scale fraud in favor of Mr. Karzai in the election on Aug. 20. According to a preliminary count, he won with 54.6% of the vote. That tally can change depending on a review of results from 12% of Afghanistan’s polling stations that was ordered by the Electoral Complaints Commission, a United Nations-sponsored watchdog.

On Thursday, representatives from the ECC, the Afghan government’s electoral commission, and the presidential candidates met in Kabul to choose a random 10% sample from the disputed polling stations. Recounting this sample is expected to take a couple of weeks, compared with months needed for a full recount.

If Mr. Karzai’s final vote tally falls below 50% he will face a runoff against the leading challenger, Abdullah Abdullah, a former foreign minister.

Time is of the essence: Such a runoff election will be virtually impossible after snowfall makes many rural roads impassable in early November.

Some Western officials called for flanking Mr. Karzai with a powerful chief executive who will run the government, while others have pushed for a unity government that would include Dr. Abdullah.

But the president’s allies cautioned that any foreign effort to disempower Mr. Karzai could plunge the country into more bloodshed. “Let’s be practical — what is the alternative to Karzai?” said Mr. Wardak. Any U.S. move against Mr. Karzai, he said, “will be seen by the Afghan population as no different from the U.S.S.R. occupation” — and trigger a similar response. By Yaroslav Trofimov, Wall Street Journal.