US Secretary of Defense Chuck Hagel has said that President Obama has asked the military to "prepare options for all contingencies" as the crisis in Syria deepens following reports of a chemical weapons attack by that country's government earlier this week.

Speaking in Malaysia Sunday, where he was starting a planned one-week tour of Asia, Hagel said that the administration was still weighing whether or not to use military force against the government of Syrian President Bashar al-Assad. Among the factors being discussed, Hagel said, were an intelligence assessment of the attack as well as possible international support for a military operation and what he described as legal issues.

"President Obama has asked the Defense Department to prepare options for all contingencies. We have done that and we are prepared to exercise whatever option -- if he decides to employ one of those options,'' Hagel said.

Obama had met earlier Saturday with top national security advisers, but will continue to gather facts before deciding on a course of action, the White House said.

Meanwhile Fox News has confirmed that four U.S. Navy Destroyers are being pre-positioned in the eastern Mediterranean Sea, although no immediate instructions beyond deployment have been issued.

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A senior State Department official also told Fox News that U.S. Secretary of State John Kerry spoke Saturday with the foreign ministers of the United Arab Emirates, Saudi Arabia, Jordan, and Turkey, as well as the Secretary of the Arab League to discuss the allegation of a chemical weapons attack by the regime of Bashar al-Assad. Kerry also spoke to Syrian foreign minister Walid al-Muallim Thursday to say that the Syrian government should allow an international weapons inspection team to visit the site in the eastern suburbs of Damascus, rather than continue to attack the area, thus blocking access and destroying any potential evidence. Kerry also told Muallim that he had received assurances from the rebel Free Syrian Army that the UN inspectors would receive safe conduct to and from the area.

Syria's government has warned that any U.S.-led military action would be "no picnic," as Syrian Information Minister Omran Zoabi told the country's official news agency, SANA. Zoabi added "U.S. military intervention will create a very serious fallout and a ball of fire that will inflame the Middle East," according to Reuters. Zoabi also told SANA that the Assad government would not allow inspectors to visit the site as it was not on a previously agreed list of sites where allegations of chemical warfare had been made against Assad's troops.

However, Iranian state TV reported Sunday that the Syrian government had told Tehran it would allow inspectors to visit the site of the reported attack. According to Reuters, Iran's Press TV reported that Mohammed Javad Zarif spoke to his Italian counterpart Emma Bonino by phone Saturday and said "We are in close contact with the Syrian government and they have reassured us that they had never used such inhumane weapons and would have the fullest cooperation with the U.N. experts to visit the areas affected."

Also Sunday, the deputy chief of staff of Iran's armed forces appeared to warn the US against taking military action in Syria. Massoud Jazayeri was quoted by the Fars news agency as saying "America knows the limitation of the red line of the Syrian front and any crossing of Syria's red line will have severe consequences for the White House,'' according to Reuters.

Also Sunday, prominent Israeli Cabinet ministers called for a US-led response, though the type of response they sought was not specified. Prime Minister Benjamin Netanyahu called the alleged chemical attack a "terrible crime," and told his Cabinet Sunday that "this situation cannot continue", according to the Associated Press. Justice Minister Tzipi Livni told Israel Radio that a US response to the alleged poison gas attack would help discourage future chemical weapons use, but also have security implications for Israel.

Intelligence Minister Yuval Steinitz told Army Radio the attack required a response. He said the chances that Syria would attack Israel as a result of US action were slim but that the army should be prepared for such an eventuality.

The reports of thousands killed or stricken by chemical weapons Wednesday near Damascus are merely the latest allegations about such tactics in the Middle East country's roughly 2-year-long civil war.

The president said last year that the use of chemical weapons by Syrian President Bashar Assad would "cross a red line." But the White House has been reluctant to take direct military actions, instead supplying rebel forces with non-lethal aid, weighing military options and trying to garner innernational support.

In Saturday's meeting, the president and his National Security Council considered eyewitness accounts and medical-records reports but "the U.S. intelligence community continues to gather facts to ascertain what occurred," the White House said.

Obama also discussed the Syria situation Saturday with British Prime Minister David Cameron.

According to the White House, the leaders expressed their "grave concern" about the reported use of chemical weapons and promised to continue to consult closely about "possible responses by the international community."

The White House meeting was attended by at least 15 members of the president’s security council including Vice President Joe Biden, Kerry, and Hagel, who participated via video conference from Kuala Lumpur.

Hagel suggested Friday that the Pentagon might move Naval forces closer to Syria in preparation for a possible decision by Obama to order military strikes.

However, a senior U.S. defense officials told the Associated Press that the Navy has already sent a fourth warship armed with ballistic missiles into the eastern Mediterranean Sea, but without immediate orders for any missile launch into Syria.

U.S. Navy ships are capable of a variety of military action, including launching Tomahawk cruise missiles, as they did against Libya in 2011 as part of an international action that led to the overthrow of the Libyan government.

Syrian state media accused rebels of using chemical arms against government troops in clashes Saturday near Damascus, while Doctors Without Borders said it has tallied 355 deaths from the purported chemical weapons attack on Wednesday.

The international aid group said three hospitals it supports in the eastern Damascus region reported receiving roughly 3,600 patients with "neurotoxic symptoms" over less than three hours on Wednesday morning when the attack in the eastern Ghouta area took place. Of those, 355 died.

The state media said Saturday the army offensive in Jobar, near Damascus, had forced the rebels to resort to chemical weapons "as their last card." State TV broadcast images of plastic jugs, gas masks, vials of an unspecified medication, explosives and other items that it said were seized from rebel hideouts. It did not, however, show any video of soldiers reportedly affected by toxic gas in the fighting.

Obama acknowledged in a CNN interview earlier this week that the episode is a "big event of grave concern" that requires American attention. He said any large-scale chemical weapons usage would affect "core national interests" of the United States and its allies. But nothing he said signaled a shift toward U.S. action.

During an interview earlier this week with CNN, the president made no mention of the red line that U.S. intelligence officials say has been breached at least on a small scale several times since.

U.S. confirmation took more than four months after rebels similarly reported chemical attacks in February, though in this instance a U.N. chemical weapons team is already on the ground in Syria. Assad's government, then as now, has denied the claims as baseless.

James Rosen and Jennifer Griffin of Fox News, The Associated Press, and Reuters contributed to this report.