"Their purpose is to support an international coalition as it takes all necessary measures to enforce the terms of UN Security Council Resolution 1973. These limited US actions will set the stage for further action by other coalition partners," Obama said in a letter to Republican House Speaker John Boehner and Senate President Pro Tempore Daniel Inouye.
UN Security Council Resolution 1973 authorised member states to take all necessary measures to protect civilians and civilian populated areas under threat of attack in Libya, including the establishment and enforcement of a "no-fly zone" in the airspace of Libya.
"United States military efforts are discrete and focused on employing unique US military capabilities to set the conditions for our European allies and Arab partners to carry out the measures authorized by the UN Security Council Resolution," he said.
Noting that Libyan leader Muammar Gaddafi was provided a very clear message that a cease-fire must be implemented immediately, Obama said the international community made it clear that all attacks against civilians had to stop; Gaddafi had to stop his forces from advancing on Benghazi; pull them back from Ajdabiya, Misrata, and Zawiya; and establish water, electricity, and gas supplies to all areas.
Finally, humanitarian assistance had to be allowed to reach the people of Libya.
"Although Gaddafi`s Foreign Minister announced an immediate cease-fire, Gaddafi and his forces made no attempt to implement such a cease-fire, and instead continued attacks on Misrata and advanced on Benghazi," Obama explained.
Gaddafi`s continued attacks and threats against civilians and civilian populated areas are of grave concern to neighbouring Arab nations and, as expressly stated in UN Security Council Resolution 1973, constitute a threat to the region and to international peace and security.
"His illegitimate use of force not only is causing the deaths of substantial numbers of civilians among his own people, but also is forcing many others to flee to neighbouring countries, thereby destabilizing the peace and security of the region," he said.
Obama said left unaddressed, the growing instability in Libya could ignite wider instability in the Middle East, with dangerous consequences to the national security interests of the US.
"Gaddafi`s defiance of the Arab League, as well as the broader international community moreover, represents a lawless challenge to the authority of the Security Council and its efforts to preserve stability in the region," he said adding that Gaddafi has forfeited his responsibility to protect his own citizens and created a serious need for immediate humanitarian assistance and protection, with any delay only putting more civilians at risk.
Obama told lawmakers that the US has not deployed ground forces into Libya and that the US forces are conducting a limited and well-defined mission in support of international efforts to protect civilians and prevent a humanitarian disaster.
"Accordingly, US forces have targeted the Gaddafi regime`s air defense systems, command and control structures, and other capabilities of Gaddafi`s armed forces used to attack civilians and civilian populated areas," he said.
"We will seek a rapid, but responsible, transition of operations to coalition, regional, or international organizations that are postured to continue activities as may be necessary to realize the objectives of UN Security Council Resolutions 1970 and 1973," Obama said.