TRIPOLI, Libya—Before U.S., U.K. and other allied forces attacked Libya's air defenses Saturday, the mood among top officials here in the capital was nothing short of surreal—a mix of denial, defiance and conciliation.

In the morning, as Col. Moammar Gadhafi's forces pounded the rebel-controlled city of Benghazi in the east, an official read a letter from the Libyan leader to French President Nicolas Sarkozy, British Prime Minister David Cameron and United Nations Secretary General Ban Ki-moon.

In the letter, Col. Gadhafi called "invalid" a U.N. resolution passed last week authorizing the use of force against the regime in order to halt its slaughter of rebels and opposition figures. Col. Gadhafi warned that they would live to "regret" any military action against Libya.