U.S. naval forces edged closer to Syria on Saturday as President Barack Obama weighed possible military options for responding to the alleged use of chemical weapons by the Assad government.

Obama has previously emphasized that a quick intervention in the Syrian civil war is problematic, given the international considerations that should precede a military strike.

Nonetheless, the president met with his national security team Saturday to consider possible next steps by the United States. It comes as the United Nation's disarmament chief Angela Kane arrived in Damascus to further press the Assad regime into allowing weapons inspectors access to the purported site of a chemical assault earlier this week.

“The President has directed the intelligence community to gather facts and evidence so that we can determine what occurred in Syria,” a White House official told reporters .

“We have a range of options available, and we are going to act very deliberately so that we're making decisions consistent with our national interest as well as our assessment of what can advance our objectives in Syria.”

Following the shift of U.S. naval forces toward Syria, Defense Secretary Chuck Hagel acknowledged that Obama had asked the Pentagon to prepare military options for Syria without going into specifics. U.S. defense officials told The Associated Press that the Navy had sent a fourth warship armed with ballistic missiles into the eastern Mediterranean Sea but without immediate orders for any missile launch into Syria.

"The Defense Department has a responsibility to provide the president with options for contingencies, and that requires positioning our forces, positioning our assets, to be able to carry out different options — whatever options the president might choose," Hagel told reporters traveling with him to Asia.

Hagel said the U.S. is coordinating with the international community to determine "what exactly did happen" near Damascus earlier this week. According to reports, a chemical attack in a suburb of the capital killed hundreds of people. It would be the largest chemical weapons attack since Iraqi leader Saddam Hussein gassed thousands of Kurds in the town of Halabja in 1988.

On Saturday, the medical charity Doctors Without Borders (MSF) said hospitals it works with in Syria had reported thousands of patients displaying "neurotoxic symptoms" in line with mass exposure to nerve gas.

"Medical staff working in these facilities provided detailed information to MSF doctors regarding large numbers of patients arriving with symptoms including convulsions, excess saliva, pinpoint pupils, blurred vision and respiratory distress," Bart Janssens, the organization's director of operations said.

Around 3,600 patients have been treated in the three hospitals, he added. Of those 355 have reportedly died, according to MSF.

Despite the Naval fleet change and the convening of his national security team, Obama remains cautious about getting involved in a war that has killed more than 100,000 people and now includes Hezbollah and al-Qaeda.