Obama said NATO will take over full control of operations in Libya on Wednesday [Al Jazeera]

US president Barack Obama has defended America's involvement in a military campaign against Muammar Gaddafi's regime in Libya in a televised address to the nation.

Speaking to military officers and reporters at the National Defence University in Washington on Monday night, Obama said he refused to wait for images of the slaughter of civilians before taking action.

In blunt terms, Obama said the Western-led air campaign had stopped Gaddafi's advances and halted a slaughter that could have shaken the stability of an entire region and "stained the conscience of the entire world".

"Some nations may be able to turn a blind eye to atrocities in other countries. The United States of America is different," Obama said.

"To brush aside America's responsibility as a leader and more profoundly our responsibilities to our fellow human beings under such circumstances would have been a betrayal of who we are."

"I can report that we have stopped Gaddafi's deadly advance," the US president said.

"We will deny the regime arms, cut off its supply of cash, assist the opposition, and work with other nations to hasten the day when Gaddafi leaves power," he said.

But he added that "it [Gaddafi's departure] may not happen overnight".

Against regime change

However, he said that broadening the international mission to include regime change would be a mistake.

"If we tried to overthrow Gaddafi by force, our coalition would splinter," he said.

Obama spoke on the eve of a 35-nation conference in London to tackle the crisis in the North African oil-exporting country and weigh political options for ending Gaddafi's 41-year rule.   

Obama's challenge was to define the limited purpose and scope of the US mission in Libya for Americans preoccupied with domestic economic concerns and weary of costly wars in two other Muslim countries, Iraq and Afghanistan.

The US took the initial lead in the Western-led military action against Gaddafi, before NATO agreed to take over the operations. Obama said the US will transfer control to NATO on Wednesday.

Obama said once that transfer occurs, the risk and cost to American taxpayers will be reduced significantly.

But Al Jazeera's Patty Culhane, reporting from Washington, said Obama's speech had two striking contradictions.

"The president said we must stand alongside those who work for freedom and at the same time he said we cannot be the policemen of the world only when it applies to our national interest.

"The president [seem to] be trying to explain why we have seen a lesser response to allies like Bahrain or Yemen," she said.

Also, he said nothing about the exit strategy, our correspondent said.

"He said nothing about ... how does this end for the US military and he did not really mention anything about the cost, so this was a broad speech to the American public. but for those people, especially members of congress who have some very pointed questions, I don't know if they are going to feel if they got the answers they were looking for," she said.

Source: Al Jazeera and agencies