The United States has said the defection of Libya's foreign minister Moussa Koussa would provide critical intelligence about Muammar Gaddafi's mental state and military plans.
As British officials debriefed Koussa after his flight to London late Wednesday, the White House also reiterated a senior official's earlier assessment that his decision was a major blow to Gaddafi's government.
National Security Council spokesman Tommy Vietor hailed a "major defection and a significant blow to the Gaddafi regime."
"Moussa Koussa is one of Gaddafi's most trusted aides who can help provide critical intelligence about Gaddafi's current state of mind and military plans.
"It also demonstrates that the people around Gaddafi understand his regime is in disarray."
The Obama administration has argued that it believes that Gaddafi's regime will eventually collapse due to massive pressure exerted by coalition air attacks on his forces, rebel action and a political and economic squeeze.
"The people around Gaddafi have to choose whether to place their bet on a regime that has lost all legitimacy and face grave consequences, or get on the right side of history," Vietor said.
"Moussa Koussa's decision shows which way the wind is blowing in Tripoli."
Mark Toner, a State Department spokesman, told reporters that the British government informed the US authorities about Koussa's defection just before it went public with the development.
But he said Jeffrey Feltman, the assistant secretary of state for Near Eastern affairs, "was not a part of the process to broker his departure and the State Department played no role in these efforts."
Feltman was informed about Koussa's defection by his British counterpart before he departed London on Wednesday, following his attendance at an international conference on Libya, Toner said.
Koussa had been in touch with Feltman recently but "at no point did it come up that he was considering leaving the regime," Toner said.
When asked if Feltman encouraged Koussa to defect, Toner replied that Feltman made clear "our desire to see Gaddafi go and the fact that these ...individuals, his regime, would be held accountable."
He added: "Yes, in the sense that we made the argument that he was part of a regime that was going nowhere."
When pressed on whether Feltman made the argument directly, Toner replied: "I believe Assistant Secretary Feltman said that."
