PARIS  The authorities in London withheld a formal response on Friday to a reported accusation by a senior Afghan official that the British introduced an impostor posing as a high Taliban commander into the presidential palace in Kabul to meet President Hamid Karzai.

News of the embarrassing ruse emerged earlier this week in an article in The New York Times saying that a man identifying himself as Mullah Akhtar Muhammad Mansour, one of the most senior commanders in the Taliban movement, had held three meetings with NATO and Afghan officials, encouraging hopes of a negotiated settlement to a nine-year war.

The fake Taliban leader even met with President Karzai, after being flown to Kabul on a NATO aircraft and ushered into the presidential palace, officials told The Times.

The episode underscored the uncertain and even bizarre nature of the atmosphere in which Afghan and American leaders are searching for ways to bring the American-led war to an end.