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David Cameron: "We have got to prepare for what we might have to do if Gaddaffi goes on brutalising his own people"
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The world cannot "stand aside" and allow violent repression to continue in Libya, David Cameron has told the BBC.
The prime minister said he spoke to US President Barack Obama on Tuesday as forces loyal to Libyan leader Col Gaddafi launched more air strikes.
Mr Cameron revealed they discussed a "full spectrum of possible responses", including a no-fly zone over Libya.
Foreign Secretary William Hague earlier said a no-fly zone was a practical possibility but needed broad support.
He said the UK and France were drafting a UN resolution relating to a no-fly zone.
Mr Cameron told BBC One's The One Show he had discussed preparations for future options with the US president.
He said: "We have got to prepare for what we might have to do if he [Gaddafi] goes on brutalising his own people.
"I had a phone call with President Obama this afternoon to talk about the planning we have to do in case this continues and in case he [Gaddafi] does terrible things to his own people. I don't think we can stand aside and let that happen."
Number 10 said the telephone conversation with the White House agreed the objectives of securing an "immediate end to brutality and violence", and the departure of Col Gaddafi.
A Downing Street spokesman said: "The prime minister and the president agreed to press forward with planning, including at Nato, on the full spectrum of possible responses, including surveillance, humanitarian assistance, enforcement of the arms embargo, and a no-fly zone.
"They committed to close co-ordination on next steps."
Mr Hague faced criticism after a botched SAS mission in Libya last week but he pledged to continue to seek solutions for "momentous events".
Labour had accused the government of "serial bungling" over the attempt to make contact with those leading opposition to the rule of Col Gaddafi.
Six soldiers and two others described as Foreign Office officials were detained for two days by rebels in eastern Libya but were freed on Sunday and left the country.
Addressing the criticism, and questions from former Liberal Democrat leader Sir Menzies Campbell over his enthusiasm for the job of foreign secretary, Mr Hague said: "These are historic times and momentous events are taking place.
"All of us who have taken on the job of shouldering responsibilities at this time must see those responsibilities through an extended period of time in the face of any criticism or setbacks.... that's how I feel about it."
Mr Hague said plans to impose no-fly zone over Libya to ensure Col Gaddafi's aircraft were kept grounded needed "clear legal basis, demonstrable need, strong international support, and broad support in the region and a readiness to participate in it".
He said: "What we call for is for Gaddafi to go, for people in Libya to be able to have the representative and broadly based government they want.
"But, of course, if that scenario changes, if it goes in other directions, well, then we have to look at other options as well, but I think we are not in that position yet."
The foreign secretary was speaking at a joint news conference with Palestinian leader Mahmoud Abbas at the Foreign Office in London.
Mr Hague added that uprisings in the Middle East and North Africa must not be allowed to derail the Middle East peace talks between Israel and the Palestinian Authority.
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