CAIRO // The countdown was under way last night to a US-led military strike against the Assad regime in response to last week's chemical attack in Damascus.
Syrian rebel chiefs said they expected intervention "within days" and the Pentagon defence chief Chuck Hagel said the US Navy had four destroyers in the eastern Mediterranean Sea within range of targets inside Syria, and US warplanes were in the region.
Barack Obama asked military chiefs to give him "all options for all contingencies", Mr Hagel said, and "we have done that".
"We are prepared. We have moved assets in place to be able to comply with whatever option the president wishes to take."
The White House said military action would not be an attempt to depose Bashar Al Assad. "The options we are considering are not about regime change," the White House spokesman Jay Carney said. "They are about responding to a clear violation of an international standard that prohibits the use of chemical weapons."
The Arab League yesterday joined most western countries in blaming the Assad regime for the chemical weapon attack that killed hundreds in a rebel-held suburb of Damascus.
The league urged the UN Security Council to "overcome the differences among its members by taking the necessary … resolutions against the perpetrators of this crime, for which the Syrian regime bears responsibility, and to end the violations and crimes of genocide that the Syrian regime has been carrying out for over two years".
Russia and China have vetoed UN measures against the Assad regime for two years. Russia in particular argues that western powers abused a resolution in 2011 to justify military action to help topple the Libyan leader Muammar Qaddafi.
Diplomatic sources said yesterday's strongly worded Arab League statement had been encouraged by Arabian Gulf states in the knowledge that air strikes were being discussed.
The Saudi foreign minister Saud Al Faisal yesterday urged the international community to take a "serious and decisive" stand against Mr Al Assad.
UN weapons inspectors are in Damascus gathering evidence of the chemical attack, although they are not expected to attribute blame. They delayed a second trip to the site yesterday because of security concerns.
The Syrian opposition said the West had consulted it over a potential military strike. "There is no precise timing … but one can speak of an imminent international intervention against the regime. It's a question of days and not weeks," said Ahmad Ramadan, a Syrian National Coalition political committee member. "There have been meetings between the Coalition, the rebel Free Syrian Army and allied countries during which possible targets have been discussed." Mr Ramadan said they included airports, military bases and arms depots.
Syria's foreign minister said his country would defend itself using "all means available". He also challenged Washington to present proof backing up its accusations that chemical weapons had been used.
Walid Al Moallem likened US allegations that the regime was behind the attack to American charges that Iraq possessed weapons of mass destruction before the 2003 US-led invasion.
"They have a history of lies - Iraq," he said. Mr Al Moallem spoke a day after John Kerry, the US secretary of state, said there was "undeniable" evidence of a large-scale chemical attack launched by the regime.
The Russian Interfax news agency said the Damascus government had adequate air defence systems to rebuff attacks.
"If the US army together with Nato launch an operation against Syria there won't be an easy victory," a military source told the agency.
Western defence experts say that US-led action would be undertaken to minimise potential casualties.
"The likelihood of small scale, precision strikes using Tomahawk cruise missiles has significantly increased since Britain, France and the US essentially accused Assad of using chemical weapons," said Nick de Larrinaga, Europe Editor of IHS Jane's Defence Weekly.
"It's about the least worst option," said a European defence source. "No one wants the risk of pilots being captured or killed."
Manned aircraft could still be used - Israeli jets have already raided Syrian targets on several occasions, proving it is possible, and US F-16s have remained in Jordan after an exercise this year.
Jordan, however, said yesterday its territory would not be a "launch pad" for military intervention.
The Jordanian government has repeatedly called for a political solution and its comments came on the second and final day of a meeting of senior military officers to discuss the regional effect of the war in Syria.
"Jordan's position has not changed. Jordanian territories will not be used as launch pad for any military action against Damascus," a senior government official said.
Support for an international military response is likely to grow if it is confirmed that the Assad regime was responsible for the attack.
The British prime minister David Cameron recalled parliament for an urgent discussion tomorrow on a possible military response, as the army drew up contingency plans.
Mr Cameron's office said Britain was considering a "proportionate" response that would deter Mr Al Assad from using chemical weapons in the future.
The French president Francois Hollande said his country was prepared to take action against those responsible for the chemical attack. "France is ready to punish those who took the heinous decision to gas innocents" , Mr Hollande said. "I have decided to increase our military support to the National Syrian Coalition."
* Reuters with additional reporting by Agence France-Presse and Associated Press