Senior Bush administration officials are angry over US Ambassador to the United Nations Zalmay Khalilzad's "unauthorised contacts" with Pakistani presidential candidate and PPP leader Asif Ali Zardari, a media report said on Tuesday.

Khalilzad had spoken by telephone with Zardari several times a week for the past month until he was confronted about the unauthorised contacts, the New York Times said, citing a senior United States official.

Other officials were quoted as saying Khalilzad had planned to meet with Zardari privately next Tuesday while on vacation in Dubai, in a session that was cancelled only after Richard A Boucher, the Assistant Secretary of State for South Asia, learned from Zardari himself that the ambassador was providing "advice and help."

"Can I ask what sort of 'advice and help' you are providing?" Boucher wrote in an angry e-mail message to Khalilzad. "What sort of channel is this? Governmental, private, personal?" the Times said.

Copies of the message, the paper said, were sent to others at the highest levels of the State Department. The Times said the message was provided to it by an administration official who had received a copy.

Officially, the US has remained neutral in the contest to succeed Musharraf and there is concern within the State Department that the discussions between Khalilzad and Zardari, could leave the impression that the United States is taking sides in Pakistan's internal politics, the Times said.

Khalilzad, the Times said, also had a close relationship with Benazir Bhutto, flying with her last summer on a private jet to a policy gathering in Aspen, Colorado. Bhutto was assassinated in Pakistan in December.

The conduct by Khalilzad, who is Afghan by birth, has also raised hackles because of speculation that he might seek to succeed Hamid Karzai as president of Afghanistan, the paper noted.

Khalilzad, who was the Bush administration's first ambassador to Afghanistan, has also kept in close contact with Afghan officials, angering William Wood, the current American ambassador, unidentified officials were quoted as saying.

Khalilzad has said he has no plans to seek the Afghan presidency. Through his spokesman, he told the Times that he had been friends with Zardari for years.

"Ambassador Khalilzad had planned to meet socially with Zardari during his personal vacation," said Richard A Grenell, the spokesman for the United States Mission to the United Nations.

"But because Zardari is now a presidential candidate, Ambassador Khalilzad postponed the meeting, after consulting senior State Department officials and Zardari himself," he added.

A senior American official was quoted as saying Khalilzad had been advised to "stop speaking freely" to Zardari and that it was not clear whether he would face any disciplinary action.

In 1979, the Times recalled, Andrew Young was forced to resign as the American ambassador to the United Nations over his unauthorised contacts with the Palestine Liberation Organization.

The Times said administration officials described John D Negroponte, the Deputy Secretary of State, and Boucher as angry over the conduct of Khalilzad because as United Nations ambassador he has no direct responsibility for American relations with Pakistan.

Those dealings have been handled principally by Negroponte, Boucher and Anne W Patterson, the American ambassador to Pakistan. Both Negroponte and Patterson served as the United Nations ambassador.