UNITED NATIONS - The United States Ambassador to the United Nations Zalmay Khalilzad has defended his "social" contacts with Asif Ali Zardari, PPP co-chairman and a leading candidate for Pakistan's presidency, saying he never acted as adviser to him. "I have not provided him with any advice," Khalilzad told reporters at UN Headquarters in New York on Wednesday, a day after returning from his vacation. "The contacts have been social contacts for the most part." According to press reports, some State Department officials were angered to learn that he had "unauthorised contacts" with Zardari, including multiple recent telephone calls and plans for a recent meeting that was concealed. The New York Times first reported last month on the internal Bush administration uneasiness over some of the Afghan-born Khalilzad's contacts. He said his friendship with the Bhutto family preceded his role in the US government. He was friends with late Benazir Bhutto and through her he had come to know her husband. After Ms Bhutto's assassination, he said he remained in touch with Zardari but those contacts were not so frequent as depicted in newspaper reports. Khalilzad's comments were his first public comments on the controversy. He had been on vacation when the stories about him first appeared. "I wanted to set the record straight," he said. "I have many contacts and friends around the world. I have been in the business a long time. Many of them precede my assignment, my role in the US government. Just because I am a government official now does not mean I should end those friendship and relationships I have had with many people." Khalilzad said he's since spoken with Secretary of State Condoleezza Rice and Assistant Secretary of State Richard Boucher about the situation, but would not disclose details of those conversations. "When something of a policy-related issue has been raised, and that has been very rare, I have reported those to the secretary and to other relevant officials. I believe that these contacts are perfectly natural; I've been surprised by the commentary or characterization of those contacts." Questioned about his phone contacts with Zardari, Khalilzad said he was experienced enough not to convey any advice on an open line on behalf of the United States. Replying to another question, he said he was not a candidate for the upcoming presidential elections in Afghanistan and that at the end of his current assignment, he would work in the private sector. "I am a permanent representative of the United States to the UN. I am proud of my job. I'm an American. And I not a candidate for the post of Afghan president." About the growing civilian casualties resulting from US-led military operations in Afghanistan, he said a joint investigation involving Afghan government, NATO and UN would take place to establish facts.