WASHINGTON In an about-turn, President Barrack Obama sent a letter to tough-talking Afghan President Hamid Karzai this week expressing support for their partnership and confirming plans to meet with him in Washington in May, The Los Angeles Times reported Friday, citing a senior administration official. The overture represented a sharp departure from the administrations recent harsh treatment of Karzai. The White House within the last week called complaints by Karzai about the United States troubling and said his planned trip in May could be cancelled. The letter was respectful and direct, and Obama pledged to continue our common effort to make Afghanistan a success, White House National Security Advisor James Jones told reporters returning with Obama to the US from Prague. We ought to calm the rhetoric and engage as strategic partners intent on bringing about peace and security, not only in Afghanistan and Pakistan, but in the region as well, Jones added. White House officials did not explain the reasons for the change in tone. But Defence officials had expressed alarm that Washington risked undermining the Afghan governments support for crucial US initiatives, such as an upcoming offensive in Kandahar. One military official said Karzai had lashed out at the United States because American officials had embarrassed him in front of his people. Such public criticism of Karzai weakens him politically and makes him a less-effective leader, the military official said. Although questions remain about the countrys 2009 presidential election, which was marred by voter fraud, US interests are best served by helping establish Karzai as a viable leader, the official said. The note, hand-delivered by the US ambassador in Kabul, thanked Karzai for his hospitality on Obamas recent visit to Afghanistan and recommitted the US to the success of our operation in Afghanistan, Jones said. Tensions flared after Obamas surprise trip to Kabul last month. He urged Karzai to act more decisively to root out corruption in his government. Karzai soon responded with sharp public remarks about too much Western involvement in Afghan affairs and suggested that his government could legitimise the Taliban. Jones said Friday that he did not believe Karzai intended to create any damage to the relationship.