Now, NATO officials are seriously considering three options, each with down sides. One is that no Afghan leader would attend. Another is to have both presidential candidates attend together. The third would be to have Mr. Karzai, who remains in office until a new inauguration, attend. That would make him the longest-serving world leader at the meeting, but one with soured relations with many NATO allies.

“There would be no benefit for him to go and no benefit for us to have him there,” said a Western diplomat with knowledge of the discussions about the meeting’s attendance.

Mr. Karzai’s spokesman, Aimal Faizi, seemed to concur with that thought. “President Karzai is not willing to attend the meeting in Wales,” he said. “It is because his views and his position on the continuation of U.S. and NATO military presence beyond 2014 in Afghanistan are known and understood. There is no change in that, and the conditions are the same.”

Mr. Faizi said that Mr. Karzai had written to the NATO secretary general, and quoted him as saying, “The people of Afghanistan will be represented at the Wales meeting either by my successor, who I hope will be inaugurated before the upcoming meeting, or by the current government.”

Mr. Karzai reportedly had a meeting on Sunday with both candidates, and told them that he thought it would be a good idea if they both went to Wales together if the audit was still continuing, according to Western diplomats and campaign officials.

Officials with the Ghani campaign said that both candidates were planning to attend the conference, and that Mr. Ghani and Mr. Abdullah met to talk in person on Tuesday night.

That meeting was said to be the fourth time the men had been in a room together since the disputed runoff vote in June. The two hugged for cameras to seal the deal reached with Mr. Kerry in July. But there has been little accord since then.

Under the Kerry deal, both candidates agreed to abide by the results of the audit as to who would be president, and then to form a government of national unity with the loser choosing the “chief executive” of the new government. But Mr. Abdullah has now threatened to back out of the audit. And officials with both campaigns said that negotiations over the unity government were still bogged down over what powers the new post of chief executive would actually have.