Syrian president Bashar Assad should be allowed a safe passage out of the country if that would end the bloodshed, David Cameron has said.
The Prime Minister said it “could be arranged” for him to flee and potentially escape international justice over the bloody repression.
But he made clear that Britain would not offer any such haven.
He opened up the possibility of an arranged exit as he prepared for talks with King Abdullah of Saudi Arabia in Jeddah.
The continuing Syrian fighting is high on the agenda for the two G20 leaders, as well as Iran and Middle East security.
Asked what he would say if President Assad said he wanted a safe exit, Mr Cameron told Al Arabiya television: “Done. Anything, anything to get that man out of the country and to have a safe transition in Syria.
“Of course, I would favour him facing the full force of international law and justice for what he’s done.
“I am certainly not offering him an exit plan to Britain but if wants to leave, he could leave, that could be arranged.”
Mr Cameron ruled out the UK arming the Syrian rebels amid accusations by the Assad regime that the Saudis and other Gulf states are doing that.
Britain would increase its humanitarian help, he said, expressing “frustration” that the international community had not done more to prevent the deaths of up to 40,000 people.
“I am very frustrated that we can’t do more. This is an appalling slaughter that is taking place in our world today – 40,000 lives lost already and you can see, on your television screens, night after night, helicopters, aeroplanes belonging to the Assad regime pounding his own country and murdering his own people. We must ask ourselves what more can we do: how can we help the opposition?
“How can we put the pressure on Assad? How can we work with partners in the region to turn this around?”
Asked about arming the rebels, he said: “We are not currently planning to do that. We are a government under international law and we obey the law. My fear is, firstly, that the slaughter will continue, that the loss of life will continue. That should be our number one concern.
“But there is another fear, which is that the longer this goes on, the more that it can promote and drive extremism and we’ll see instability in the region as well.”
Mr Cameron is using his visit to Saudi Arabia – his second as Prime Minister – to continue his push for trade deals and investment, including Typhoon fighter jets.
Human rights groups have criticised the arms sales push because of allegations of serious violations.
Saudi officials reacted angrily to the recent announcement that the Commons Foreign Affairs Committee was to examine the country’s record.
“It is my job to get good deals for Britain, which means jobs in the UK, investment in the UK and make sure that we’re in the global race, but at the same time not compromising on our strong views about human rights, which we raise with all of these countries,” Mr Cameron said.
“But let’s be clear, I came here to the United Arab Emirates wanting the strongest possible long-term defence partnership between our two countries and that’s exactly what we’ve agreed with Typhoon, and that is a very good outcome for both our countries and for jobs in the UK.
“Now when it comes to Saudi Arabia, again this is a country that’s very important for our prosperity but it’s also important for our security too.”