Prime Minister David Cameron is to challenge world leaders to seize the "massive opportunity" presented by the Arab Spring, as he flies the flag for interventionism.
At the United Nations general assembly in New York, Mr Cameron will say the "historic" events in Libya and across the Arab states of northern Africa show that the UN "needs a new way of working".
The PM will argue that "where action is necessary", the UN should step in at all times. "To fail to act is to fail those who need our help," he will tell delegates.
Drawing on the experience of the Arab Spring and his own visits to the region, Mr Cameron will say that events have provided "a massive opportunity to spread peace, prosperity, democracy and vitally security" but only if nations seize it.
He will continue: "The UN has to show that we can be not just united in condemnation, but united in action, acting in a way that lives up to the UN's founding principles and meet the needs of the people."
In a call for greater action among member states, Mr Cameron will ask: "You can sign every human rights declaration in the world, but if you stand by and watch people being slaughtered in their own country, when you could act, then what are those signatures really worth?"
He will argue that the people of the Arab world have made their aspirations clear, in that they desire greater freedom, more accountable governments and an end to corruption. Moreover, it is a global obligation to help them achieve these goals, Mr Cameron will suggest.
On Wednesday, Mr Cameron met US president Barack Obama at the UN as Palestinians prepares to bid for statehood. He held talks with the US President as the Government weighs its response to an expected push by Palestinian president Mahmoud Abbas on Friday.
Speaking at the start of their bilateral talks, Mr Obama said he was "very fortunate" that he and Mr Cameron had developed "an excellent friendship" over the past 16 months.
President Obama added: "We are keenly interested in finding a resolution to the Israeli/Palestinian conflict.