Senior White House officials have begun to make the case for a policy shift in Afghanistan that would send few, if any, new combat troops to the country and instead focus on faster military training of Afghan forces, continued assassinations of al-Qaeda leaders and support for the government of neighboring Pakistan in its fight against the Taliban.

In a three-hour meeting Wednesday at the White House, senior advisers challenged some of the key assumptions in Gen. Stanley A. McChrystal’s blunt assessment of the nearly eight-year-old war, which President Obama has said is being fought to destroy al-Qaeda and its allies in Afghanistan and the ungoverned border areas of Pakistan…

But White House officials are resisting McChrystal’s call for urgency, which he underscored Thursday during a speech in London, and questioning important elements of his assessment, which calls for a vast expansion of an increasingly unpopular war. One senior administration official, speaking on the condition of anonymity to discuss the meeting, said, “A lot of assumptions — and I don’t want to say myths, but a lot of assumptions — were exposed to the light of day.”