DAMASCUS, Syria -- The Syrian government accused rebels of using chemical weapons Saturday and warned the United States not to launch any military action against Damascus over an alleged chemical attack last week, saying such a move would set the Middle East ablaze.
 
   The accusations by the regime of President Bashar Assad against opposition forces came as an international aid group said it has tallied 355 deaths from a purported chemical weapons attack on Wednesday in a suburb of the Syrian capital known as Ghouta.
 
   Syria is intertwined in alliances with Iran, Lebanese Hezbollah guerrillas and Palestinian militant groups. The country also borders its longtime foe and U.S. ally Israel, making the fallout from military action unpredictable.
 
   Violence in Syria has already spilled over the past year to Lebanon, Turkey, Iraq and the Israeli-occupied Golan Heights. Battle-hardened Hezbollah fighters have joined the combat alongside Assad's forces.
 
   Meanwhile, U.S. naval units are moving closer to Syria as President Barack Obama considers a military response to the alleged use of chemical weapons by Assad's government.
 
   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 officials spoke on condition of anonymity because they weren't authorized to discuss ship movements publicly.
 
   Obama emphasized that a quick intervention in the Syrian civil war was problematic, given the international considerations that should precede a military strike.
 
   After Obama met with his national security team Saturday, the White House said U.S. intelligence officials are still trying to determine whether Assad's government unleashed the chemical weapons attack earlier this week.
 
   The White House statement said Obama received a detailed review of the range of options he has requested for the U.S. and the international community to respond if it is determined that Assad has engaged in deadly chemical warfare.
 
   Obama spoke by telephone with British Prime Minister David Cameron about Syria, the White House said.
 
   A statement from Cameron's office at No. 10 Downing St. said the prime minister and Obama are concerned by ``increasing signs'' that ``a significant chemical weapons attack'' was carried out by the Syrian government against its people. Obama and Cameron ``reiterated that significant use of chemical weapons would merit a serious response from the international community,'' according to the statement.
 
   Syria's Information Minister Omran al-Zoubi dismissed the possibility of an American attack, warning that such a move would risk triggering more violence in the region.
 
   ``The basic repercussion would be a ball of fire that would burn not only Syria but the whole Middle East,'' al-Zoubi said in an interview with Lebanon-based Al-Mayadeen TV. ``An attack on Syria would be no easy trip.''
 
   In Tehran, Iran's Foreign Ministry Spokesman, Abbas Arakji, warned that an American military intervention in Syria will ``complicate matters.''
 
   ``Sending warships will not solve the problems but will worsen the situation,'' Arakji said in comments carried by Iran's Arabic-language TV Al-Alam. He added that any such U.S. move does not have international backing and that Iran ``rejects military solutions.''
 
   In France, Doctors Without Borders 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 Paris-based group said.
 
   The Britain-based Syrian Observatory for Human Rights said Saturday that its estimated death toll from the alleged chemical attack had reached 322, including 54 children, 82 women and dozens of fighters. It said the dead included 16 people who have not been identified.
 
   The group said it raised its death toll from an earlier figure of 136, which had been calculated before its activists in the stricken areas met doctors, residents and saw medical reports. It said the dead ``fell in the massacre committed by the Syrian regime.''
 
   Death tolls have varied wildly over the alleged attack, with Syrian anti-government activists reporting between 322 and 1,300 killed. (AP)