By Patricia Zengerle and Steve Holland
WASHINGTON (Reuters) - President Barack Obama sought to reassure Americans about U.S. military involvement in Libya on Saturday, saying the mission is limited and the United States will not intervene everywhere there is a crisis.
Obama, accused by many lawmakers of failing to explain U.S. objectives in Libya, used his weekly radio and Web address to speak about his Libyan policy and plans a Monday night address to the American people to explain it further.
So far, polls show Americans back the president for using U.S. air power and cruise missiles to attack Libyan leader Muammar Gaddafi's air defenses and other targets aimed at supporting Libyan rebels and protecting civilians from government forces.
A Reuters-Ipsos poll in recent days said 60 percent of Americans back him on Libya, although only 17 percent saw him as a strong and decisive leader. A Gallup poll put American support for his Libyan move at 47 percent, with 37 percent disapproving.
"We're succeeding in our mission," Obama said. "Because we acted quickly, a humanitarian catastrophe has been avoided and the lives of countless civilians -- innocent men, women and children -- have been saved."
Easing some pressure on Obama, NATO is expected to take over command and control of the week-old allied military operation this weekend from the United States.
"Our military has provided unique capabilities at the beginning, but this is now a broad, international effort," he said, noting that Arab partners like Qatar and the United Arab Emirates have committed aircraft.
Obama was cautious on the potential for U.S. intervention elsewhere, as Americans now see news reports of unrest convulsing Syria and Yemen.
"As commander in chief, I face no greater decision than sending our military men and women into harm's way. And the United States should not -- and cannot -- intervene every time there's a crisis somewhere in the world," he said.
Analyst Larry Sabato, a University of Virginia political science professor, said Obama was late in explaining what is at in Libya to Americans weary of wars in Iraq and Afghanistan.
"The long and short of it is he's getting around now to what he should've done before military action began," he said.
Sabato said Obama, who plans to seek re-election in 2012, faces potentially troublesome outcomes in Libya.
"We've been lucky there have been no American or allied casualties. But that could change. The cost could mount, and this could turn into a stalemate," he said.
Ipsos pollster Julia Clark the cost of the war could become an issue if it rises.
"Americans still prioritize the economy as the biggest issue right now," she said. "Foreign aid is among the least popular expenditures for taxpayer dollars."
Obama said the role of U.S. forces has been clear and focused and limited in what he described as a "broad, international effort." He stressed again that no U.S. ground forces would go into Libya.
Members of Congress -- from both the left and right -- have criticized Obama for failing to communicate thoroughly the goals of the military operation. Some have assailed him for failing to seek congressional approval for the action, others for embarking on another military mission in a Muslim country when the United States is already embroiled in the Iraq and Afghan wars.
Obama reiterated that Gaddafi must stop attacking civilians, pull back his forces and allow humanitarian assistance to reach those who need it. He said Gaddafi has lost the confidence of the Libyan people and the legitimacy to rule, but did not call directly for Gaddafi's removal, which Washington has said repeatedly is not the purpose of the military mission.
(Editing by Doina Chiacu)