By Alister Bull and Missy Ryan
BRASILIA/WASHINGTON (Reuters) - U.S. forces joined those of four other countries in launching military action against Libya on Saturday, and President Barack Obama said U.S. involvement was limited and only in support of an international effort.
The United States, France, Britain, Canada and Italy began launching strikes designed to cripple Muammar Gaddafi's air defenses, as the West tries to force the Libyan leader from power. At least some Arab nations are expected to join the coalition later.
Announcing that the strikes had begun, Obama said the effort was intended to protect the Libyan people.
"Today I authorized the armed forces of the United States to begin a limited action in Libya in support of an international effort to protect Libyan civilians. That action has now begun," Obama told reporters in Brasilia, where he has just begun a five-day tour of Latin American.
He said U.S. troops were acting in support of allies, who will lead the enforcement of a no-fly zone. French warplanes began operations over Libya earlier on Saturday to stop Gaddafi's attacks on rebels.
"As I said yesterday, we will not, I repeat, we will not deploy any U.S. troops on the ground," Obama said, grim-faced as he delivered the news of U.S. military action in a third Muslim country.
Missiles were launched from a warship against targets in the oil-producing North African country.
U.S. forces and planes will take part in the operation, called "Odyssey Dawn," which will mainly target air defenses around the Libyan cities of Tripoli and Misrata.
Some 25 coalition ships, including three U.S. submarines armed with Tomahawk missiles, and are stationed in the Mediterranean, a military slide showed. Five U.S. surveillance planes are also in the area, it showed.
The United States is already enmeshed in long wars in Afghanistan and Iraq and there is little appetite in Congress and among the public for another expensive military intervention. U.S. officials have said repeatedly that it is time for Gaddafi to leave, but lately have stressed that the goal of military action in Libya was different.
"It is to protect civilians and it is to provide access for humanitarian assistance," Secretary of State Hillary Clinton said in Paris, where she attended a conference called by French President Sarkozy to discuss the international response to the Libya crisis.
(Additional reporting by Matt Spetalnick in Brasilia, Phil Stewart in Washington and Andrew Quinn in Paris; Writing by Patricia Zengerle; editing by Doina Chiacu)