NEW DELHI: The Central Intelligence Agency (CIA) has concluded that Islamic State (IS) militants, operating in Iraq and Syria, can “can muster between 20,000 and 31,500 fighters.” This estimate is more than double a previous CIA estimate, that had pinned the number of IS fighters at 10,000.

"This new total reflects an increase in members because of stronger recruitment since June following battlefield successes and the declaration of a caliphate, greater battlefield activity, and additional intelligence," a CIA spokesperson reportedly told CNN.

The estimate follows a speech by United States President Barack Obama on the eve of the September 11 attacks, that outlined a four step strategy to combat IS, which will considerably deepen American involvement in the Middle East, and begin a long-term, open-ended conflict that Obama’s presidential campaign had vowed to avoid.

The strategy comprised of air strikes, support to on-the-ground forces, counter terrorism efforts and humanitarian aid. In reference to an expanded role of air strikes, Obama indicated that action will not be limited to Iraq. “I have made it clear that we will hunt down terrorists who threaten our country, wherever they are. That means I will not hesitate to take action against ISIL in Syria as well as Iraq,” the President said.

A CNN report quoted another unnamed US official saying that the US was already conducting surveillance flights within Syria’s borders, looking to collect information that will enable it to take a decision on air strikes in the future.

Pentagon spokesperson Adm. John Kirby said that whenever the US does decide to conduct air strikes in Syria, it will consider targeting individuals in leadership positions. “One of the ways you get at and you destroy the capabilities of an enemy like (ISIS) is to be pretty aggressive against them, and that does include disrupting their ability to command and control and to lead their own forces," Kirby said.

Whilst airstrikes in Iraqi territory are not a contentious issue as they are supported by the newly formed Iraqi government, that is, in turn, supported by the US, they are a far more complicated issue within Syrian borders.

Syria immediately made a statement warning the US that any foreign intervention in the country will amount to a an act of aggression unless it is approved by Damascus. Ali Haidar, minister of national reconciliation affairs, speaking to reporters in the Syrian capital, said, “Any action of any type without the approval of Syrian government is an aggression against Syria. There must be cooperation with Syria and coordination with Syria and there must be a Syrian approval of any action whether it is military or not."

Syria has repeatedly expressed its willingness to work with foreign governments to tackle IS fighters, who are waging a war against Syrian President Bashar-al-Assad and have captured large swathes of territory in the country. Ironically, the IS’ rise in Syria was facilitated by foreign government’s in the US, who, in an attempt to topple Assad, have supported anti-government militias with aid, equipment, and training.

Although there is considerable infighting amongst the many anti-government groups, with the IS militants facing setbacks at the hands of the Islamic Front and the Free Syrian Army, for instance, there is evidence to point to the fact that IS benefited from this foreign aid and assistance in its initial days.

Obama’s strategy has received support from various other countries, including France who may join the IS-bomb club. "In Iraq... we support the formation of an inclusive government. We will participate if necessary in an aerial military action," French Foreign Minister Laurent Fabius said in a speech in Paris.

The French Foreign Minister added that whilst France was willing to work with the government in Iraq, it will not work with Assad’s government in Syria “because he has an established link" with IS. There is no indication or any evidence of Assad having a link with IS, as the Syrian government continues to try and win its territory back from anti-government militias which include the IS, and has repeatedly asserted its willingness to fight the IS.

The US also received support from ten Arab countries: Egypt, Iraq, Jordan, Lebanon and six Gulf states including Saudi Arabia and Qatar. "The participating states agreed to do their share in the comprehensive fight against ISIL, including ... as appropriate, joining in the many aspects of a coordinated military campaign against ISIL," a statement, following a meeting between Arab countries’ leaders -- which excluded Iran and Syria -- with US Secretary of State John Kerry said.

In the meanwhile, Germany ruled out the prospect of taking part in air strikes in Iraq or Syria. "To be quite clear, we have not been asked to do so and neither will we do so," German Foreign Minister Frank-Walter Steinmeier said at a news conference in Berlin. Germany however, is already providing equipment to Kurdish fighters battling IS militants in Iraq.

The United Kingdom has given a mix response, with Foreign Secretary Philip Hammond initially saying that the UK had “ruled out nothing” in reference to airstrikes and following that with a clarification that said, “Let me be clear: Britain will not be taking part in any airstrikes in Syria. We have already had that discussion in our parliament last year and we won't be revisiting that position."

Russia, in turn, has strongly condemned the prospect of air strikes in Syria, saying that such an action would be a “gross violation” of international law. "The US president has spoken directly about the possibility of strikes by the US armed forces against Isis positions in Syria without the consent of the legitimate government," Russian Foreign Ministry spokesperson Alexander Lukashevich said. "This step, in the absence of a UN security council decision, would be an act of aggression, a gross violation of international law."