Paris: As diplomats from around the world sought a global strategy to fight Isil extremists, Iran ruled out working with any international coalition, saying it had rejected American requests for cooperation against the militants.

Neither Iran nor Syria, which together share most of Iraq’s borders, was invited to the international conference on Monday in Paris, which opened as a pair of French reconnaissance jets took off over Iraqi skies.

With memories of the 2003 US invasion of Iraq still fresh, the US has so far been alone in carrying out air strikes and no country has offered ground troops. An American official said several Arab countries had offered to conduct air strikes, speaking on condition of anonymity to discuss the sensitive issue.

“The terrorist threat is global and the response must be global,” French President Francois Hollande said, opening the diplomatic conference intended to come up with an international strategy against the group. “There is no time to lose.”

The killing of David Haines, a British aid worker held hostage by the militants, added urgency to the calls for a coherent strategy against the brutal and well-organised Sunni group, which is a magnet for Muslim extremists from all over the world and rakes in more than $3 million a day from oil smuggling, human trafficking, theft and extortion, according to US intelligence officials and private experts.

Iraq’s President Fouad Massoum called for a coordinated military and humanitarian approach, as well as regular strikes against territory in the hands of the extremists and the elimination of their funding.

“There can be no sanctuary,” Massoum said. “We have to dry up their sources of financing.”

Muslim-majority countries are considered vital to any operation to prevent the militants from gaining more territory in Iraq and Syria. Western officials have made clear they consider Syrian President Bashar Al Assad part of the problem, and US officials opposed France’s attempt to invite Iran, a Shiite nation, to the conference in Paris.

Iranian Supreme leader Ayatollah Ali Khamenei, speaking on Iranian state television, said his government privately refused American requests for cooperation against Isil group, warning that another US incursion would result “in the same problems they faced in Iraq in the past 10 years.”

Ahead of the conference, France’s foreign minister acknowledged that a number of the countries at the table on Monday had “very probably” financed Isil’s advances. Iraq’s president appeared ambivalent about Arab participation, saying his country needed the support of its neighbours — but not necessarily their fighter jets or soldiers.

Speaking in his first interview since becoming Iraqi prime minister, Haider Al Abadi told state-run Al Iraqiyya in comments aired on Sunday that he had given approval to France to use Iraqi airspace and said all such authorisations would have to come from Baghdad.

British Prime Minister David Cameron said his country would continue offering logistical help to US forces and that counterterrorism efforts will increase, describing Isil group as a “massive” security threat that cannot be ignored.