UNITED NATIONS — The American ambassador to the United Nations, Zalmay Khalilzad, is cutting his vacation short and is due to return home on Monday night, after a leaked State Department memorandum raised questions about his methods of work, which many U.N. diplomats fondly call his “independent streak” but which have angered some of his colleagues in the Bush administration.

As State Department officials questioned whether Mr. Khalilzad’s communications with a top Pakistani politician, Asif Ali Zardari, were authorized by policymakers, the ambassador decided to end his vacation in Europe early. He will return to New York on Monday night, according to a State Department official who confirmed a Web log entry posted yesterday by the spokesman for the American mission, Richard Grenell.

“We were told yesterday that ambassador Khalilzad will come back home earlier than expected from his vacation — I am sure he will be confronted with more erroneous assumptions from reporters who don’t bother checking the facts,” Mr. Grenell wrote at richardgrenell.com, where he took issue with some reporting on the memorandum, which first appeared on Monday in an article in the New York Times.

“Ambassador Khalilzad is in constant touch with the State Department,” Mr. Grenell told The New York Sun yesterday. “He knows and delivers the policies of the United States.”

President Bush and Secretary of State Rice “value his counsel,” a State Department spokesman, Robert Wood, said earlier this week, adding, “Ms. Rice has full confidence in Ambassador Khalilzad.”

“Khalilzad knows many people,” the Pakistani ambassador to the United Nations, Munir Akram, said. Like many diplomats here, Mr. Akram sought to avoid speaking extensively on the topic, which is a sensitive one in Washington and Islamabad. Diplomats rushed to defend Mr. Khalilzad, who is popular among many U.N. ambassadors, including some who have serious policy differences with America.

The Times article apparently touched a nerve in Washington and according to several sources was the top item on the agenda of the White House staff meeting on Tuesday.

State Department officials, including Deputy Secretary John Negroponte, are said to be miffed about Mr. Khalilzad’s consultations with Mr. Zardari, a pro-Western politician vying for the Pakistani presidency amid a major upheaval in the country, which began when a former prime minister — and Mr. Zardari’s wife — Benazir Bhutto, was assassinated in December.

A memorandum written by the assistant secretary of state for South Asia, Richard Boucher, referred to extensive recent phone conversations between Messrs. Khalilzad and Zardari. “What sort of channel is this? Governmental, private, personnel?” Mr. Boucher wrote in the memo.