Cameron: ISIS should be ‘squeezed out of existence’

• NEW: NATO chief says request for help from Iraq to fight ISIS “would be considered seriously”
• ISIS should be “squeezed out of existence,” British Prime Minister David Cameron says
• Russian President Putin’s push into Ukraine has the 28-nation alliance focused on action
• Ukrainian President Petro Poroshenko is due to meet NATO leaders at the summit

Newport, Wales (CNN) — The world faces a “generational struggle” against the threat of Islamist extremism, and ISIS should be “squeezed out of existence,” British Prime Minister David Cameron said Thursday.

Speaking ahead of a NATO summit in Newport, Wales, Cameron told CNN that leaders meeting there would be discussing the “poisonous ideology” of Islamist extremism and how to combat it.

The summit, billed as the most important gathering of NATO leaders in more than a decade, comes at a time of global turmoil.

Also on the packed agenda for the 28-member NATO alliance is the challenge posed by Russian aggression against Ukraine, and NATO’s future role in Afghanistan.

NATO to pressure Russia over Ukraine

Cameron said NATO members should agree on how to help Middle Eastern nations such as Jordan tackle the threat posed by ISIS.

Any request by Iraq to NATO for aid in fighting against ISIS would be “considered seriously,” NATO Secretary-General Anders Fogh Rasmussen said Thursday in a NATO TV broadcast.

NATO has not yet received such an invitation from Baghdad, Rasmussen said, but help could come in the form of new military training programs such as the alliance held with Iraq in the past.

Cameron declined to rule in or out the possibility of the UK military carrying out airstrikes against ISIS forces, as U.S. forces have done in Iraq.

“We don’t rule anything out, we’ll act with partners in our national interest,” he said, adding that Britain was already helping the Kurds by providing equipment and was flying surveillance missions.

Cameron said Britain had been “working exhaustively to identify all the people that are potentially involved” in two ISIS videos showing the beheading of U.S. journalists James Foley and Steven Sotloff but would not give any further detail.

“We share our information with our key allies and (are) making sure we do everything we can to bring these absolutely horrific people to justice,” he said.

A British hostage was threatened at the end of the latest execution video, which features a militant with an English accent.

Cameron: Russia needs America, Europe

Cameron also had stern words for Russia, which annexed Ukraine’s Crimean peninsula in March and is accused of sending its troops into eastern Ukraine in support of pro-Russia rebels, a claim Moscow denies.

World security hinges on NATO

Cameron said it was “positive” that Russian President Vladimir Putin, who on Wednesday set out a seven-point roadmap to end the Ukraine conflict, was “at least making noises about peace.”

But, he said, trust has been eroded by Putin’s consistent denials that Russian troops are on Ukrainian soil, when “everyone can see that that is the case.”

The Western nations who have already imposed sanctions against Putin over Russia’s actions need to make clear that if Putin does not allow Ukraine to choose its own future, Russia’s relationship with the United States and Europe will be very different.

“And let’s be frank, Russia needs America and Europe more than America and Europe need Russia. We need to make that relationship pay.”

Ukrainian President Petro Poroshenko is due to meet NATO leaders at the summit.

Ukraine is not part of NATO, but the alliance has said it will support Kiev in the face of what it calls Russian aggression.

‘Russia has ripped up the rulebook’

U.S. President Barack Obama arrived in Wales Wednesday for the summit, after a visit to Estonia aimed at reassuring nervous Eastern European nations that NATO’s support for its member states is unwavering.

A vision of a Europe dedicated to peace and freedom is “threatened by Russia’s aggression against Ukraine,” Obama said in the Estonian capital, Tallinn.

In a joint opinion piece published in the Times of London on Thursday, Obama and Cameron say NATO “is as vital to our future as it has ever been” and warn against isolationism.

“We meet at a time when the world faces many dangerous and evolving challenges,” they write.

“To the east, Russia has ripped up the rulebook with its illegal, self-declared annexation of Crimea and its troops on Ukrainian soil threatening a sovereign nation state. To the south, there is an arc of instability from north Africa and the Sahel to the Middle East.”

The two leaders say that those who argue against getting involved in action to address these threats fail to understand security in the 21st century.

“NATO is not just an alliance of friends who come to the aid of each other in times of need. It is also an alliance based on national self-interest,” they write.

“Whether it is regional aggression going unchecked or the prospect that foreign fighters could return from Iraq and Syria to pose a threat in our countries, the problems we face today threaten the security of British and American people, and the wider world.”

Rasmussen said on Twitter that the two-day meeting in Wales “is a critical summit at a critical time. Today and tomorrow we will forge a stronger #NATO for a more complex, chaotic world.”

‘Time running out’ in Afghanistan

The summit was originally expected to focus on Afghanistan, NATO’s biggest overseas commitment of troops, before events elsewhere in the world seized the headlines.

Rasmussen warned Thursday that time is running out for NATO to be able to continue its mission in Afghanistan, as combat troops prepare to depart at the end of the year.

The role of NATO’s International Security Assistance Force in the country will shift from leading Afghan troops in the fight to supporting Afghans in an advisory and training role.

While votes in the contested presidential election are still being audited, Rasmussen said that “time is of the essence” for the Afghan government to finalize a Status of Forces Agreement to protect NATO forces there.

But he did say he was “encouraged” that both candidates in the run-off vote, Abdullah Abdullah andAshraf Ghani, have agreed on the need for a new agreement.

Rasmussen said he remained hopeful that they could work on setting up an agreement that both could support so that the next president of Afghanistan could quickly sign it.

CNN’s Nic Robertson reported in Newport and Laura Smith-Spark wrote and reported in London. CNN’s Brian Walker contributed to this report.